pygrass.vector package¶
Submodules¶
pygrass.vector.abstract module¶
Created on Fri Aug 17 17:24:03 2012
@author: pietro
-
class
pygrass.vector.abstract.
Info
(name, mapset='', *aopen, **kwopen)[source]¶ Bases:
object
Basic vector info. To get access to the vector info the map must be opened.
>>> test_vect = Info(test_vector_name) >>> test_vect.open(mode='r')
Then it is possible to read and write the following map attributes:
>>> test_vect.organization 'Thuenen Institut' >>> test_vect.person 'Soeren Gebbert' >>> test_vect.title 'Test dataset' >>> test_vect.scale 1 >>> test_vect.comment 'This is a comment' >>> test_vect.comment = "One useful comment!" >>> test_vect.comment 'One useful comment!'
There are some read only attributes:
>>> test_vect.maptype 'native'
And some basic methods:
>>> test_vect.is_3D() False >>> test_vect.exist() True >>> test_vect.is_open() True >>> test_vect.close()
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close
(build=False)[source]¶ Method to close the Vector
Parameters: build (bool) – True if the vector map should be build before close it
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comment
¶ Set or obtain the Vector comment
-
date
¶ Set or obtain the Vector date
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full_name
¶ Return the full name of Vector
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map_date
¶ Set or obtain the Vector map date
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mapset
¶ Set or obtain the Vector mapset
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maptype
¶ Return the map type of Vector
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mode
¶
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name
¶ Set or obtain the Vector name
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open
(mode=None, layer=1, overwrite=None, with_z=None, tab_name='', tab_cols=None, link_name=None, link_key='cat', link_db='$GISDBASE/$LOCATION_NAME/$MAPSET/sqlite/sqlite.db', link_driver='sqlite')[source]¶ Open a Vector map.
Parameters: - mode (str) – open a vector map in
r
in reading,w
in writing and inrw
read and write mode - layer (int) – specify the layer that you want to use
- overwrite (bool) – valid only for
w
mode - with_z (bool) – specify if vector map must be open with third dimension
enabled or not. Valid only for
w
mode, default: False - tab_name (str) – define the name of the table that will be generate
- tab_cols (list of pairs) – define the name and type of the columns of the attribute table of the vecto map
- link_name (str) – define the name of the link connecttion with the database
- link_key (str) – define the nema of the column that will be use as vector category
- link_db (str) – define the database connection parameters
- link_driver – define witch database driver will be used
- link_driver – str
Some of the parameters are valid only with mode
w
orrw
See more examples in the documentation of the
read
andwrite
methods- mode (str) – open a vector map in
-
organization
¶ Set or obtain the Vector organization
-
person
¶ Set or obtain the Vector author
-
proj
¶ Set or obtain the Vector projection code
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proj_name
¶ Return the project name of Vector
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rename
(newname)[source]¶ Method to rename the Vector map
Parameters: newname (str) – the new name for the Vector map
-
scale
¶ Set or obtain the Vector scale
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thresh
¶ Set or obtain the Vector threshold
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title
¶ Set or obtain the Vector title
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zone
¶ Set or obtain the Vector projection zone
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pygrass.vector.basic module¶
Created on Tue Jul 31 13:06:20 2012
@author: pietro
-
class
pygrass.vector.basic.
Bbox
(north=0, south=0, east=0, west=0, top=0, bottom=0)[source]¶ Bases:
object
Instantiate a Bounding Box class that contains a ctypes pointer to the C struct bound_box, that could be used by C GRASS functions.
>>> bbox = Bbox() >>> bbox Bbox(0.0, 0.0, 0.0, 0.0)
The default parameters are 0. It is possible to set or change the parameters later, with:
>>> bbox.north = 10 >>> bbox.south = -10 >>> bbox.east = -20 >>> bbox.west = 20 >>> bbox Bbox(10.0, -10.0, -20.0, 20.0)
Or directly istantiate the class with the values, with:
>>> bbox = Bbox(north=100, south=0, east=0, west=100) >>> bbox Bbox(100.0, 0.0, 0.0, 100.0)
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bottom
¶ Set and obtain bottom value
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contains
(point)[source]¶ Return True if the object is contained by the BoundingBox
Parameters: point (a Point object or a tuple with the coordinates) – the point to analyze >>> from grass.pygrass.vector.geometry import Point >>> poi = Point(5,5) >>> bbox = Bbox(north=10, south=0, west=0, east=10) >>> bbox.contains(poi) True
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east
¶ Set and obtain east value
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north
¶ Set and obtain north value
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nsewtb
(tb=True)[source]¶ Return a list of values from bounding box
Parameters: tb (bool) – if tb parameter is False return only: north, south, east, west and not top and bottom
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south
¶ Set and obtain south value
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top
¶ Set and obtain top value
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west
¶ Set and obtain west value
-
-
class
pygrass.vector.basic.
BoxList
(boxlist=None)[source]¶ Bases:
object
Instantiate a BoxList class to create a list of Bounding Box
-
append
(box)[source]¶ Append a Bbox object to a Boxlist object, using the
Vect_boxlist_append
C function.Parameters: - bbox – the bounding box to add to the list
- bbox – a Bbox object
>>> box0 = Bbox() >>> box1 = Bbox(1,2,3,4) >>> box2 = Bbox(5,6,7,8) >>> boxlist = BoxList([box0, box1]) >>> boxlist Boxlist([Bbox(0.0, 0.0, 0.0, 0.0), Bbox(1.0, 2.0, 3.0, 4.0)]) >>> len(boxlist) 2 >>> boxlist.append(box2) >>> len(boxlist) 3
-
ids
¶
-
n_values
¶
-
remove
(indx)[source]¶ Remove Bbox from the boxlist, given an integer or a list of integer or a boxlist, using
Vect_boxlist_delete
C function or theVect_boxlist_delete_boxlist
.Parameters: - indx – the index value of the Bbox to remove
- indx – int
>>> boxlist = BoxList([Bbox(), ... Bbox(1, 0, 0, 1), ... Bbox(1, -1, -1, 1)]) >>> boxlist.remove(0) >>> boxlist Boxlist([Bbox(1.0, 0.0, 0.0, 1.0), Bbox(1.0, -1.0, -1.0, 1.0)])
-
-
class
pygrass.vector.basic.
Cats
(c_cats=None)[source]¶ Bases:
object
Instantiate a Category class that contains a ctypes pointer to the C line_cats struct.
>>> cats = Cats() >>> for cat in range(100, 110): cats.set(cat, layer=cat-50) >>> cats.n_cats 10 >>> cats.cat [100, 101, 102, 103, 104, 105, 106, 107, 108, 109] >>> cats.layer [50, 51, 52, 53, 54, 55, 56, 57, 58, 59] >>> cats.get() # default layer is 1 (-1, 0) >>> cats.get(50) (100, 1) >>> cats.get(51) (101, 1) >>> cats.set(1001, 52) >>> cats.cat [100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 1001] >>> cats.layer [50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 52] >>> cats.get(52) (102, 2) >>> cats.reset() >>> cats.layer [] >>> cats.cat []
-
cat
¶
-
check_cats_constraints
(cats_list, layer=1)[source]¶ Check if categories match with category constraints
Parameters: - cats_list (list) – a list of categories
- layer (int) – the number of layer
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delete
(cat=None, layer=1)[source]¶ If cat is given delete cat from line_cats structure (using Vect_field_cat_del) else delete all categories of given layer (using Vect_cat_del).
Parameters: - cat (int) – the cat to add
- layer (int) – the number of layer
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get
(layer=1)[source]¶ Return the first found category of given layer and the number of category found.
Parameters: layer (int) – the number of layer
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get_list
(layer=1)[source]¶ Get list of categories of given field.
Parameters: layer (int) – the number of layer
-
layer
¶
-
n_cats
¶ Return the number of categories
-
-
class
pygrass.vector.basic.
CatsList
(c_cat_list=None)[source]¶ Bases:
object
>>> cats_list = CatsList() >>> cats_list.min [] >>> cats_list.max [] >>> cats_list.n_ranges 0 >>> cats_list.layer 0 >>> string = "2,3,5-9,20" >>> cats_list.from_string(string) >>> cats_list.min [2, 3, 5, 20] >>> cats_list.max [2, 3, 9, 20] >>> cats_list.n_ranges 4
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from_array
(array)[source]¶ Convert ordered array of integers to cat_list structure.
Parameters: array (array) – the input array containing the cats
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from_string
(string)[source]¶ Converts string of categories and cat ranges separated by commas to cat_list.
Parameters: string (str) – a string containing the cats separated by commas
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layer
¶ Return the layer number
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max
¶ Return the maximum value
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min
¶ Return the minimum value
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n_ranges
¶ Return the ranges number
-
-
class
pygrass.vector.basic.
Ilist
(integer_list=None)[source]¶ Bases:
object
Instantiate a list of integer using the C GRASS struct
ilist
, the class contains this struct asc_ilist
attribute.
pygrass.vector.find module¶
Created on Tue Mar 19 11:09:30 2013
@author: pietro
-
class
pygrass.vector.find.
AbstractFinder
(c_mapinfo, table=None, writeable=False)[source]¶ Bases:
object
-
class
pygrass.vector.find.
BboxFinder
(c_mapinfo, table=None, writeable=False)[source]¶ Bases:
pygrass.vector.find.AbstractFinder
Bounding Box finder
This class provides an interface to search geometry features of a vector map that are inside or intersect a boundingbox. The BboxFinder class is part of a topological vector map object.
-
areas
(bbox, boxlist=None, bboxlist_only=False)[source]¶ Find areas inside a boundingbox.
Parameters: - bbox (grass.pygrass.vector.basic.Bbox) – The boundingbox to search in
- boxlist – An existing BoxList to be filled with
- bboxlist_only (boolean) – If true the BoxList will be returned, no features are generated
Type_boxlist: grass.pygrass.vector.basic.BoxList
Returns: A list of areas or None if nothing was found
This methods uses libvect.Vect_select_areas_by_box()
Examples:
>>> from grass.pygrass.vector import VectorTopo >>> from grass.pygrass.vector.basic import Bbox >>> test_vect = VectorTopo(test_vector_name) >>> test_vect.open('r')
# Find areas in box >>> bbox = Bbox(north=5, south=-1, east=9, west=-1) >>> result = test_vect.find_by_bbox.areas(bbox=bbox) >>> [area for area in result] [Area(1), Area(2), Area(3), Area(4)]
>>> bbox = Bbox(north=5, south=-1, east=9, west=-1) >>> result = test_vect.find_by_bbox.areas(bbox=bbox, ... bboxlist_only=True) >>> result #doctest: +NORMALIZE_WHITESPACE Boxlist([Bbox(4.0, 0.0, 4.0, 0.0), Bbox(4.0, 0.0, 6.0, 4.0), Bbox(3.0, 1.0, 3.0, 1.0), Bbox(4.0, 0.0, 8.0, 6.0)])
>>> bbox = Bbox(north=20, south=18, east=20, west=18) >>> test_vect.find_by_bbox.areas(bbox=bbox)
>>> test_vect.find_by_bbox.areas(bbox=bbox, ... bboxlist_only=True)
>>> test_vect.close()
-
geos
(bbox, type='all', bboxlist_only=False)[source]¶ Find vector features inside a boundingbox.
Parameters: - bbox (grass.pygrass.vector.basic.Bbox) – The boundingbox to search in
- type (string) – The type of feature to search for Valid type are all the keys in find.vtype dictionary
- bboxlist_only (boolean) – If true the BoxList will be returned, no features are generated
Returns: A list of grass.pygrass.vector.geometry (Line, Point, Boundary, Centroid) if found, or None if nothing was found. If bboxlist_only is True a BoxList object will be returned, or None if nothing was found.
This methods uses libvect.Vect_select_lines_by_box()
Examples:
>>> from grass.pygrass.vector import VectorTopo >>> from grass.pygrass.vector.basic import Bbox >>> test_vect = VectorTopo(test_vector_name) >>> test_vect.open('r')
>>> bbox = Bbox(north=5, south=-1, east=3, west=-1) >>> result = test_vect.find_by_bbox.geos(bbox=bbox) >>> [bbox for bbox in result] #doctest: +NORMALIZE_WHITESPACE [Boundary([Point(4.000000, 0.000000), Point(0.000000, 0.000000)]), Boundary([Point(0.000000, 0.000000), Point(0.000000, 4.000000)]), Boundary([Point(0.000000, 4.000000), Point(4.000000, 4.000000)]), Boundary([Point(1.000000, 1.000000), Point(1.000000, 3.000000), Point(3.000000, 3.000000), Point(3.000000, 1.000000), Point(1.000000, 1.000000)]), Centroid(2.500000, 2.500000)]
>>> bbox = Bbox(north=5, south=-1, east=3, west=-1) >>> result = test_vect.find_by_bbox.geos(bbox=bbox, ... bboxlist_only=True) >>> result #doctest: +NORMALIZE_WHITESPACE Boxlist([Bbox(0.0, 0.0, 4.0, 0.0), Bbox(4.0, 0.0, 0.0, 0.0), Bbox(4.0, 4.0, 4.0, 0.0), Bbox(3.0, 1.0, 3.0, 1.0), Bbox(2.5, 2.5, 2.5, 2.5)])
>>> bbox = Bbox(north=7, south=-1, east=15, west=9) >>> result = test_vect.find_by_bbox.geos(bbox=bbox) >>> [bbox for bbox in result] #doctest: +NORMALIZE_WHITESPACE [Line([Point(10.000000, 4.000000), Point(10.000000, 2.000000), Point(10.000000, 0.000000)]), Point(10.000000, 6.000000), Line([Point(12.000000, 4.000000), Point(12.000000, 2.000000), Point(12.000000, 0.000000)]), Point(12.000000, 6.000000), Line([Point(14.000000, 4.000000), Point(14.000000, 2.000000), Point(14.000000, 0.000000)]), Point(14.000000, 6.000000)]
>>> bbox = Bbox(north=20, south=18, east=20, west=18) >>> test_vect.find_by_bbox.geos(bbox=bbox)
>>> bbox = Bbox(north=20, south=18, east=20, west=18) >>> test_vect.find_by_bbox.geos(bbox=bbox, bboxlist_only=True)
>>> test_vect.close()
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islands
(bbox, bboxlist_only=False)[source]¶ Find isles inside a boundingbox.
Parameters: - bbox (grass.pygrass.vector.basic.Bbox) – The boundingbox to search in
- bboxlist_only (boolean) – If true the BoxList will be returned, no features are generated
Returns: A list of isles or None if nothing was found
This methods uses libvect.Vect_select_isles_by_box()
Examples:
>>> from grass.pygrass.vector import VectorTopo >>> from grass.pygrass.vector.basic import Bbox >>> test_vect = VectorTopo(test_vector_name) >>> test_vect.open('r')
# Find isles in box >>> bbox = Bbox(north=5, south=-1, east=9, west=-1) >>> result = test_vect.find_by_bbox.islands(bbox=bbox) >>> [isle for isle in result] [Isle(1), Isle(2)]
>>> bbox = Bbox(north=5, south=-1, east=9, west=-1) >>> result = test_vect.find_by_bbox.islands(bbox=bbox, ... bboxlist_only=True) >>> result #doctest: +NORMALIZE_WHITESPACE Boxlist([Bbox(4.0, 0.0, 8.0, 0.0), Bbox(3.0, 1.0, 3.0, 1.0)])
>>> bbox = Bbox(north=20, south=18, east=20, west=18) >>> test_vect.find_by_bbox.islands(bbox=bbox)
>>> test_vect.find_by_bbox.islands(bbox=bbox, ... bboxlist_only=True)
>>> test_vect.close()
-
nodes
(bbox)[source]¶ Find nodes inside a boundingbox.
Parameters: bbox (grass.pygrass.vector.basic.Bbox) – The boundingbox to search in Returns: A list of nodes or None if nothing was found This methods uses libvect.Vect_select_nodes_by_box()
Examples:
>>> from grass.pygrass.vector import VectorTopo >>> from grass.pygrass.vector.basic import Bbox >>> test_vect = VectorTopo(test_vector_name) >>> test_vect.open('r')
# Find nodes in box >>> bbox = Bbox(north=5, south=-1, east=15, west=9) >>> result = test_vect.find_by_bbox.nodes(bbox=bbox) >>> [node for node in result] [Node(2), Node(1), Node(4), Node(3), Node(5), Node(6)]
>>> bbox = Bbox(north=20, south=18, east=20, west=18) >>> test_vect.find_by_bbox.nodes(bbox=bbox)
>>> test_vect.close()
-
-
class
pygrass.vector.find.
PointFinder
(c_mapinfo, table=None, writeable=False)[source]¶ Bases:
pygrass.vector.find.AbstractFinder
Point finder
This class provides an interface to search geometry features of a vector map that are close to a point. The PointFinder class is part of a topological vector map object.
-
area
(point)[source]¶ Find the nearest area around a specific point.
Parameters: point (grass.pygrass.vector.geometry.Point) – The point to search Returns: A grass.pygrass.vector.geometry.Area if found or None This methods uses libvect.Vect_find_area()
Examples:
>>> from grass.pygrass.vector import VectorTopo >>> from grass.pygrass.vector.geometry import Point >>> test_vect = VectorTopo(test_vector_name) >>> test_vect.open('r')
# Find AREAS >>> points = (Point(0.5,0.5), Point(5,1), Point(7,1)) >>> result = [] >>> for point in points: … area = test_vect.find_by_point.area(point) … result.append(area) >>> result [Area(1), Area(2), Area(4)] >>> for area in result: … print(area.to_wkt()) #doctest: +NORMALIZE_WHITESPACE POLYGON ((0.0000000000000000 0.0000000000000000,
0.0000000000000000 4.0000000000000000, 0.0000000000000000 4.0000000000000000, 4.0000000000000000 4.0000000000000000, 4.0000000000000000 4.0000000000000000, 4.0000000000000000 0.0000000000000000, 4.0000000000000000 0.0000000000000000, 0.0000000000000000 0.0000000000000000),- (1.0000000000000000 1.0000000000000000,
- 3.0000000000000000 1.0000000000000000, 3.0000000000000000 3.0000000000000000, 1.0000000000000000 3.0000000000000000, 1.0000000000000000 1.0000000000000000))
- POLYGON ((4.0000000000000000 0.0000000000000000,
- 4.0000000000000000 4.0000000000000000, 4.0000000000000000 4.0000000000000000, 6.0000000000000000 4.0000000000000000, 6.0000000000000000 4.0000000000000000, 6.0000000000000000 0.0000000000000000, 6.0000000000000000 0.0000000000000000, 4.0000000000000000 0.0000000000000000))
- POLYGON ((6.0000000000000000 0.0000000000000000,
- 6.0000000000000000 4.0000000000000000, 6.0000000000000000 4.0000000000000000, 8.0000000000000000 4.0000000000000000, 8.0000000000000000 4.0000000000000000, 8.0000000000000000 0.0000000000000000, 8.0000000000000000 0.0000000000000000, 6.0000000000000000 0.0000000000000000))
>>> test_vect.find_by_point.area(Point(20,20))
>>> test_vect.close()
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geo
(point, maxdist, type='all', exclude=0)[source]¶ Find the nearest vector feature around a specific point.
Parameters: - point (grass.pygrass.vector.geometry.Point) – The point to search
- maxdist (float) – The maximum search distance around the point
- type (string) – The type of feature to search for Valid type are all the keys in find.vtype dictionary
- exclude – if > 0 number of lines which should be excluded from selection
Returns: A grass.pygrass.vector.geometry.Node if found or None
This methods uses libvect.Vect_find_line()()
Examples:
>>> from grass.pygrass.vector import VectorTopo >>> from grass.pygrass.vector.geometry import Point >>> test_vect = VectorTopo(test_vector_name) >>> test_vect.open('r')
# Find single features >>> points = (Point(10,0), Point(10,6), Point(14,2)) >>> result = [] >>> for point in points: … f = test_vect.find_by_point.geo(point=point, maxdist=1) … if f: … result.append(f) >>> for f in result: … print(f.to_wkt_p()) #doctest: +NORMALIZE_WHITESPACE LINESTRING(10.000000 4.000000,
10.000000 2.000000, 10.000000 0.000000)POINT(10.000000 6.000000) LINESTRING(14.000000 4.000000,
14.000000 2.000000, 14.000000 0.000000)>>> test_vect.find_by_point.geo(point=Point(20,20), maxdist=0)
>>> test_vect.close()
-
geos
(point, maxdist, type='all', exclude=None)[source]¶ Find the nearest vector features around a specific point.
Parameters: - point (grass.pygrass.vector.geometry.Point) – The point to search
- maxdist (float) – The maximum search distance around the point
- type (string) – The type of feature to search for Valid type are all the keys in find.vtype dictionary
- exclude – if > 0 number of lines which should be excluded from selection
Returns: A list of grass.pygrass.vector.geometry (Line, Point, Boundary, Centroid) if found or None
This methods uses libvect.Vect_find_line_list()()
Examples:
>>> from grass.pygrass.vector import VectorTopo >>> from grass.pygrass.vector.geometry import Point >>> test_vect = VectorTopo(test_vector_name) >>> test_vect.open('r')
# Find multiple features >>> points = (Point(10,0), Point(10,5), Point(14,2)) >>> result = [] >>> for point in points: … f = test_vect.find_by_point.geos(point=point, … maxdist=1.5) … if f: … result.append(f) >>> for f in result: … print(f) #doctest: +NORMALIZE_WHITESPACE [Line([Point(10.000000, 4.000000),
Point(10.000000, 2.000000), Point(10.000000, 0.000000)])]- [Line([Point(10.000000, 4.000000),
- Point(10.000000, 2.000000), Point(10.000000, 0.000000)]),
Point(10.000000, 6.000000)]
- [Line([Point(14.000000, 4.000000),
- Point(14.000000, 2.000000), Point(14.000000, 0.000000)])]
# Find multiple boundaries >>> point = Point(3,3) >>> result = test_vect.find_by_point.geos(point=Point(3,3), … type=”boundary”, … maxdist=1.5) >>> result #doctest: +NORMALIZE_WHITESPACE [Boundary([Point(0.000000, 4.000000), Point(4.000000, 4.000000)]),
Boundary([Point(4.000000, 4.000000), Point(4.000000, 0.000000)]), Boundary([Point(1.000000, 1.000000), Point(1.000000, 3.000000),
Point(3.000000, 3.000000), Point(3.000000, 1.000000), Point(1.000000, 1.000000)]),Boundary([Point(4.000000, 4.000000), Point(6.000000, 4.000000)])]
# Find multiple centroids >>> point = Point(3,3) >>> result = test_vect.find_by_point.geos(point=Point(3,3), … type=”centroid”, … maxdist=1.5) >>> result #doctest: +NORMALIZE_WHITESPACE [Centroid(2.500000, 2.500000),
Centroid(3.500000, 3.500000)]>>> test_vect.find_by_point.geos(point=Point(20,20), maxdist=0)
>>> test_vect.close()
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island
(point)[source]¶ Find the nearest island around a specific point.
Parameters: point (grass.pygrass.vector.geometry.Point) – The point to search Returns: A grass.pygrass.vector.geometry.Isle if found or None This methods uses Vect_find_island.Vect_find_area()
Examples:
>>> from grass.pygrass.vector import VectorTopo >>> from grass.pygrass.vector.geometry import Point >>> test_vect = VectorTopo(test_vector_name) >>> test_vect.open('r')
# Find ISLANDS >>> points = (Point(2,2), Point(5,1)) >>> result = [] >>> for point in points: … area = test_vect.find_by_point.island(point) … result.append(area) >>> result [Isle(2), Isle(1)] >>> for isle in result: … print(isle.to_wkt()) #doctest: +NORMALIZE_WHITESPACE Polygon((1.000000 1.000000, 3.000000 1.000000,
3.000000 3.000000, 1.000000 3.000000, 1.000000 1.000000))- Polygon((0.000000 4.000000, 0.000000 0.000000, 4.000000 0.000000,
- 6.000000 0.000000, 8.000000 0.000000, 8.000000 4.000000, 6.000000 4.000000, 4.000000 4.000000, 0.000000 4.000000))
>>> test_vect.find_by_point.island(Point(20,20))
>>> test_vect.close()
-
node
(point, maxdist)[source]¶ Find the nearest node around a specific point.
Parameters: - point (grass.pygrass.vector.geometry.Point) – The point to search
- maxdist (float) – The maximum search distance around the point
Returns: A grass.pygrass.vector.geometry.Node if found or None
This methods uses libvect.Vect_find_node()()
Examples:
>>> from grass.pygrass.vector import VectorTopo >>> from grass.pygrass.vector.geometry import Point >>> test_vect = VectorTopo(test_vector_name) >>> test_vect.open('r')
# Find nearest node >>> points = (Point(10,0), Point(10,4), Point(14,0)) >>> result = [] >>> for point in points: … f = test_vect.find_by_point.node(point=point, maxdist=1) … if f: … result.append(f) >>> result [Node(2), Node(1), Node(6)]
>>> test_vect.find_by_point.node(point=Point(20,20), maxdist=0)
>>> test_vect.close()
-
pygrass.vector.geometry module¶
Created on Wed Jul 18 10:46:25 2012
@author: pietro
-
class
pygrass.vector.geometry.
Area
(**kargs)[source]¶ Bases:
pygrass.vector.geometry.Geo
Vect_build_line_area, Vect_find_area, Vect_get_area_box, Vect_get_area_points_geos, Vect_centroid_area,
Vect_get_isle_area, Vect_get_line_areas, Vect_get_num_areas, Vect_get_point_in_area, Vect_isle_find_area, Vect_point_in_area, Vect_point_in_area_outer_ring,
Vect_read_area_geos, Vect_remove_small_areas, Vect_select_areas_by_box, Vect_select_areas_by_polygon
-
area
()[source]¶ Returns area of area without areas of isles. double Vect_get_area_area (const struct Map_info *Map, int area)
-
bbox
(bbox=None)[source]¶ Return the Bbox of area
Parameters: bbox (a Bbox object) – a Bbox object to fill with info from bounding box of area
-
boundaries
(ilist=False)[source]¶ Creates list of boundaries for given area.
- int Vect_get_area_boundaries(const struct Map_info *Map,
- int area, struct ilist *List)
-
buffer
(dist=None, dist_x=None, dist_y=None, angle=0, round_=True, caps=True, tol=0.1)[source]¶ Return the buffer area around the area, using the
Vect_area_buffer2
C function.Parameters: - dist (num) – the distance around the area
- dist_x (num) – the distance along x
- dist_y (num) – the distance along y
- angle (num) – the angle between 0x and major axis
- round (bool) – to make corners round
- tol (float) – fix the maximum distance between theoretical arc and output segments
Returns: the buffer as line, centroid, isles object tuple
-
cat
¶
-
cats
(cats=None)[source]¶ Get area categories.
Parameters: cats (a Cats object) – a Cats object to fill with info with area categories
-
centroid
()[source]¶ Return the centroid
Parameters: centroid (a Centroid object) – a Centroid object to fill with info from centroid of area
-
contains_point
(point, bbox=None)[source]¶ Check if point is in area.
Parameters: - point (a Point object or a tuple with the coordinates) – the point to analyze
- bbox (a Bbox object) – the bounding box where run the analysis
-
get_first_cat
()[source]¶ Find FIRST category of given field and area.
int Vect_get_area_cat(const struct Map_info *Map, int area, int field)
..warning: Not implemented
-
gtype
= 64¶
-
perimeter
()[source]¶ Calculate area perimeter.
Returns: double Vect_area_perimeter (const struct line_pnts *Points)
-
points
(line=None)[source]¶ Return a Line object with the outer ring
Parameters: line (a Line object) – a Line object to fill with info from points of area
-
read
()[source]¶ Read and set the coordinates of the centroid from the vector map, using the centroid_id and calling the Vect_read_line C function
-
-
class
pygrass.vector.geometry.
Attrs
(cat, table, writeable=False)[source]¶ Bases:
object
-
cat
¶ Set and obtain cat value
-
-
class
pygrass.vector.geometry.
Boundary
(**kargs)[source]¶ Bases:
pygrass.vector.geometry.Line
-
area
()[source]¶ Return the area of the polygon.
>>> bound = Boundary(points=[(0, 0), (0, 2), (2, 2), (2, 0), ... (0, 0)]) >>> bound.area() 4.0
-
gtype
= 4¶
-
left_area_id
¶ Left side area id, only available after read_area_ids() was called
-
left_centroid
(idonly=False)[source]¶ Return left centroid
Parameters: idonly (bool) – True to return only the cat of feature
-
right_area_id
¶ Right side area id, only available after read_area_ids() was called
-
-
class
pygrass.vector.geometry.
Centroid
(area_id=None, **kargs)[source]¶ Bases:
pygrass.vector.geometry.Point
The Centroid class inherit from the Point class. Centroid contains an attribute with the C Map_info struct, and attributes with the id of the Area.
>>> centroid = Centroid(x=0, y=10) >>> centroid Centroid(0.000000, 10.000000) >>> from grass.pygrass.vector import VectorTopo >>> test_vect = VectorTopo(test_vector_name) >>> test_vect.open(mode='r') >>> centroid = Centroid(v_id=18, c_mapinfo=test_vect.c_mapinfo) >>> centroid Centroid(3.500000, 3.500000) >>> test_vect.close()
-
gtype
= 8¶
-
-
class
pygrass.vector.geometry.
Geo
(v_id=0, c_mapinfo=None, c_points=None, c_cats=None, table=None, writeable=False, is2D=True, free_points=False, free_cats=False)[source]¶ Bases:
object
Base object for different feature types
-
cat
¶
-
gtype
= None¶
-
read
()[source]¶ Read and set the coordinates of the centroid from the vector map, using the centroid_id and calling the Vect_read_line C function
-
-
class
pygrass.vector.geometry.
Isle
(**kargs)[source]¶ Bases:
pygrass.vector.geometry.Geo
An Isle is an area contained by another area.
-
class
pygrass.vector.geometry.
Line
(points=None, **kargs)[source]¶ Bases:
pygrass.vector.geometry.Geo
Instantiate a new Line with a list of tuple, or with a list of Point.
>>> line = Line([(0, 0), (1, 1), (2, 0), (1, -1)]) >>> line Line([Point(0.000000, 0.000000), Point(1.000000, 1.000000), Point(2.000000, 0.000000), Point(1.000000, -1.000000)])
-
alive
()[source]¶ Return True if this line is alive or False if this line is dead or its index is out of range.
-
append
(pnt)[source]¶ Appends one point to the end of a line, using the
Vect_append_point
C function.Parameters: pnt – the point to add to line Like python list.
-
bbox
(bbox=None)[source]¶ Return the bounding box of the line, using
Vect_line_box
C function.>>> line = Line([(0, 0), (0, 1), (2, 1), (2, 0)]) >>> bbox = line.bbox() >>> bbox Bbox(1.0, 0.0, 2.0, 0.0)
-
buffer
(dist=None, dist_x=None, dist_y=None, angle=0, round_=True, caps=True, tol=0.1)[source]¶ Return the buffer area around the line, using the
Vect_line_buffer2
C function.Parameters: - dist (num) – the distance around the line
- dist_x (num) – the distance along x
- dist_y (num) – the distance along y
- angle (num) – the angle between 0x and major axis
- round (bool) – to make corners round
- tol (float) – fix the maximum distance between theoretical arc and output segments
Returns: the buffer as Area object
>>> line = Line([(0, 0), (0, 2)]) >>> boundary, centroid, isles = line.buffer(10) >>> boundary #doctest: +ELLIPSIS Line([Point(-10.000000, 0.000000),...Point(-10.000000, 0.000000)]) >>> centroid #doctest: +NORMALIZE_WHITESPACE Point(0.000000, 0.000000) >>> isles []
-
delete
(indx)[source]¶ Remove the point in the index position. :param indx: the index where add new point :type indx: int
>>> line = Line([(0, 0), (1, 1), (2, 2)]) >>> line.delete(-1) >>> line #doctest: +NORMALIZE_WHITESPACE Line([Point(0.000000, 0.000000), Point(1.000000, 1.000000)])
-
distance
(pnt)[source]¶ Calculate the distance between line and a point.
Parameters: pnt (a Point object or a tuple with the coordinates) – the point to calculate distance Return a namedtuple with:
- point: the closest point on the line,
- dist: the distance between these two points,
- spdist: distance to point on line from segment beginning
- sldist: distance to point on line form line beginning along line
The distance is compute using the
Vect_line_distance
C function.>>> point = Point(2.3, 0.5) >>> line = Line([(0, 0), (2, 0), (3, 0)]) >>> line.distance(point) #doctest: +NORMALIZE_WHITESPACE LineDist(point=Point(2.300000, 0.000000), dist=0.5, spdist=0.2999999999999998, sldist=2.3)
-
extend
(line, forward=True)[source]¶ Appends points to the end of a line.
Parameters: - line (Line object ot list of points) – it is possible to extend a line, give a list of points, or directly with a line_pnts struct.
- forward – if forward is True the line is extend forward otherwise is extend backward. The method use the Vect_append_points C function.
-
first_cat
()[source]¶ Fetches FIRST category number for given vector line and field, using the
Vect_get_line_cat
C function.Warning
Not implemented yet.
-
from_wkt
(wkt)[source]¶ Create a line reading a WKT string.
Parameters: wkt – the WKT string containing the LINESTRING
-
gtype
= 2¶
-
insert
(indx, pnt)[source]¶ Insert new point at index position and move all old points at that position and above up, using
Vect_line_insert_point
C function.Parameters: - indx (int) – the index where add new point
- pnt – the point to add
-
length
()[source]¶ Calculate line length, 3D-length in case of 3D vector line, using Vect_line_length C function.
>>> line = Line([(0, 0), (1, 1), (0, 1)]) >>> line.length() 2.414213562373095
-
length_geodesic
()[source]¶ Calculate line length, usig Vect_line_geodesic_length C function.
>>> line = Line([(0, 0), (1, 1), (0, 1)]) >>> line.length_geodesic() 2.414213562373095
-
nodes
()[source]¶ Return the start and end nodes of the line
This method requires topology build.
- return: A tuple of Node objects that represent the
- start and end point of this line.
-
point_on_line
(distance, angle=0, slope=0)[source]¶ Return a Point object on line in the specified distance, using the Vect_point_on_line C function. Raise a ValueError If the distance exceed the Line length.
>>> line = Line([(0, 0), (1, 1)]) >>> line.point_on_line(5) Traceback (most recent call last): ... ValueError: The distance exceed the length of the line, that is: 1.414214 >>> line.point_on_line(1) Point(0.707107, 0.707107)
-
pop
(indx)[source]¶ Return the point in the index position and remove from the Line.
Parameters: indx – the index where add new point
-
prune
()[source]¶ Remove duplicate points, i.e. zero length segments, using Vect_line_prune C function.
>>> line = Line([(0, 0), (1, 1), (1, 1), (2, 2)]) >>> line.prune() >>> line Line([Point(0.000000, 0.000000), Point(1.000000, 1.000000), Point(2.000000, 2.000000)])
-
prune_thresh
(threshold)[source]¶ Remove points in threshold, using the
Vect_line_prune_thresh
C function.Parameters: threshold – the threshold value where prune points Warning
prune_thresh is not working yet.
-
remove
(pnt)[source]¶ Delete point at given index and move all points above down, using Vect_line_delete_point C function.
Parameters: pnt – the point to remove
-
reset
()[source]¶ Reset line, using Vect_reset_line C function.
>>> line = Line([(0, 0), (1, 1), (2, 0), (1, -1)]) >>> len(line) 4 >>> line.reset() >>> len(line) 0 >>> line Line([])
-
reverse
()[source]¶ Reverse the order of vertices, using Vect_line_reverse C function.
>>> line = Line([(0, 0), (1, 1), (2, 2)]) >>> line.reverse() >>> line Line([Point(2.000000, 2.000000), Point(1.000000, 1.000000), Point(0.000000, 0.000000)])
-
segment
(start, end)[source]¶ Create line segment. using the
Vect_line_segment
C function.Parameters: - start (float) – distance from the beginning of the line where the segment start
- end (float) – distance from the beginning of the line where the segment end
- ::
# x (1, 1) # | # |- # | # x——–x (1, 0) # (0, 0) ^
>>> line = Line([(0, 0), (1, 0), (1, 1)]) >>> line.segment(0.5, 1.5) #doctest: +NORMALIZE_WHITESPACE Line([Point(0.500000, 0.000000), Point(1.000000, 0.000000), Point(1.000000, 0.500000)])
-
to_array
()[source]¶ Return an array of coordinates.
>>> line = Line([(0, 0), (1, 1), (2, 0), (1, -1)]) >>> line.to_array() array([[ 0., 0.], [ 1., 1.], [ 2., 0.], [ 1., -1.]])
-
-
class
pygrass.vector.geometry.
LineDist
(point, dist, spdist, sldist)¶ Bases:
tuple
-
dist
¶ Alias for field number 1
-
point
¶ Alias for field number 0
-
sldist
¶ Alias for field number 3
-
spdist
¶ Alias for field number 2
-
-
class
pygrass.vector.geometry.
Node
(v_id, c_mapinfo, **kwords)[source]¶ Bases:
object
Node class for topological analysis of line neighbors.
Objects of this class will be returned by the node() function of a Line object.
All methods in this class require a proper setup of the Node objects. Hence, the correct id and a valid pointer to a mapinfo object must be provided in the constructions. Otherwise a segfault may happen.
-
alive
()[source]¶ Return True if this node is alive or False if this node is dead or its index is out of range.
-
ilines
(only_in=False, only_out=False)[source]¶ Return a generator with all lines id connected to a node. The line id is negative if line is ending on the node and positive if starting from the node.
Parameters: - only_in (bool) – Return only the lines that are ending in the node
- only_out (bool) – Return only the lines that are starting in the node
-
-
class
pygrass.vector.geometry.
Point
(x=0, y=0, z=None, **kargs)[source]¶ Bases:
pygrass.vector.geometry.Geo
Instantiate a Point object that could be 2 or 3D, default parameters are 0.
>>> pnt = Point() >>> pnt.x 0.0 >>> pnt.y 0.0 >>> pnt.z >>> pnt.is2D True >>> pnt Point(0.000000, 0.000000) >>> pnt.z = 0 >>> pnt.is2D False >>> pnt Point(0.000000, 0.000000, 0.000000) >>> print(pnt) POINT Z (0.0000000000000000 0.0000000000000000 0.0000000000000000) >>> c_points = ctypes.pointer(libvect.line_pnts()) >>> c_cats = ctypes.pointer(libvect.line_cats()) >>> p = Point(c_points = c_points, c_cats=c_cats) >>> del p >>> c_points = ctypes.pointer(libvect.line_pnts()) >>> c_cats = ctypes.pointer(libvect.line_cats()) >>> p = Point(c_points=c_points, c_cats=c_cats, free_points=True, ... free_cats=True) >>> del p
-
buffer
(dist=None, dist_x=None, dist_y=None, angle=0, round_=True, tol=0.1)[source]¶ Return the buffer area around the point, using the
Vect_point_buffer2
C function.Parameters: - dist (num) – the distance around the point
- dist_x (num) – the distance along x
- dist_y (num) – the distance along y
- angle (num) – the angle between 0x and major axis
- round (bool) – to make corners round
- tol (float) – fix the maximum distance between theoretical arc and output segments
Returns: the buffer as Area object
>>> pnt = Point(0, 0) >>> boundary, centroid = pnt.buffer(10) >>> boundary #doctest: +ELLIPSIS Line([Point(10.000000, 0.000000),...Point(10.000000, 0.000000)]) >>> centroid Point(0.000000, 0.000000)
-
coords
()[source]¶ Return a tuple with the point coordinates.
>>> pnt = Point(10, 100) >>> pnt.coords() (10.0, 100.0)
If the point is 2D return a x, y tuple. But if we change the
z
the Point object become a 3D point, therefore the method return a x, y, z tuple.>>> pnt.z = 1000. >>> pnt.coords() (10.0, 100.0, 1000.0)
-
distance
(pnt)[source]¶ Calculate distance of 2 points, using the Vect_points_distance C function, If one of the point have z == None, return the 2D distance.
Parameters: pnt – the point for calculate the distance
-
gtype
= 1¶
-
to_wkt_p
()[source]¶ Return a “well know text” (WKT) geometry string Python implementation.
>>> pnt = Point(10, 100) >>> pnt.to_wkt_p() 'POINT(10.000000 100.000000)'
Warning
Only
POINT
(2/3D) are supported,POINTM
andPOINT
with:XYZM
are not supported yet.
-
x
¶ Set and obtain x coordinate
-
y
¶ Set and obtain y coordinate
-
z
¶ Set and obtain z coordinate
-
-
pygrass.vector.geometry.
get_xyz
(pnt)[source]¶ Return a tuple with: x, y, z.
>>> pnt = Point(0, 0) >>> get_xyz(pnt) (0.0, 0.0, 0.0) >>> get_xyz((1, 1)) (1, 1, 0.0) >>> get_xyz((1, 1, 2)) (1, 1, 2) >>> get_xyz((1, 1, 2, 2)) #doctest: +ELLIPSIS Traceback (most recent call last): ... ValueError: The the format of the point is not supported: (1, 1, 2, 2)
-
pygrass.vector.geometry.
intersects
(lineA, lineB, with_z=False)[source]¶ Return a list of points
>>> lineA = Line([(0, 0), (4, 0)]) >>> lineB = Line([(2, 2), (2, -2)]) >>> intersects(lineA, lineB) Line([Point(2.000000, 0.000000)])
-
pygrass.vector.geometry.
read_WKT
(string)[source]¶ Read the string and return a geometry object
WKT:
POINT(0 0) LINESTRING(0 0,1 1,1 2) POLYGON((0 0,4 0,4 4,0 4,0 0),(1 1, 2 1, 2 2, 1 2,1 1)) MULTIPOINT(0 0,1 2) MULTILINESTRING((0 0,1 1,1 2),(2 3,3 2,5 4)) MULTIPOLYGON(((0 0,4 0,4 4,0 4,0 0),(1 1,2 1,2 2,1 2,1 1)), ((-1 -1,-1 -2,-2 -2,-2 -1,-1 -1))) GEOMETRYCOLLECTION(POINT(2 3),LINESTRING(2 3,3 4))
EWKT:
POINT(0 0 0) -- XYZ SRID=32632;POINT(0 0) -- XY with SRID POINTM(0 0 0) -- XYM POINT(0 0 0 0) -- XYZM SRID=4326;MULTIPOINTM(0 0 0,1 2 1) -- XYM with SRID MULTILINESTRING((0 0 0,1 1 0,1 2 1),(2 3 1,3 2 1,5 4 1)) POLYGON((0 0 0,4 0 0,4 4 0,0 4 0,0 0 0),(1 1 0,2 1 0,2 2 0,1 2 0,1 1 0)) MULTIPOLYGON(((0 0 0,4 0 0,4 4 0,0 4 0,0 0 0), (1 1 0,2 1 0,2 2 0,1 2 0,1 1 0)), ((-1 -1 0,-1 -2 0,-2 -2 0,-2 -1 0,-1 -1 0))) GEOMETRYCOLLECTIONM( POINTM(2 3 9), LINESTRINGM(2 3 4, 3 4 5) ) MULTICURVE( (0 0, 5 5), CIRCULARSTRING(4 0, 4 4, 8 4) ) POLYHEDRALSURFACE( ((0 0 0, 0 0 1, 0 1 1, 0 1 0, 0 0 0)), ((0 0 0, 0 1 0, 1 1 0, 1 0 0, 0 0 0)), ((0 0 0, 1 0 0, 1 0 1, 0 0 1, 0 0 0)), ((1 1 0, 1 1 1, 1 0 1, 1 0 0, 1 1 0)), ((0 1 0, 0 1 1, 1 1 1, 1 1 0, 0 1 0)), ((0 0 1, 1 0 1, 1 1 1, 0 1 1, 0 0 1)) ) TRIANGLE ((0 0, 0 9, 9 0, 0 0)) TIN( ((0 0 0, 0 0 1, 0 1 0, 0 0 0)), ((0 0 0, 0 1 0, 1 1 0, 0 0 0)) )
pygrass.vector.sql module¶
It is a collection of strings to avoid to repeat the code.
>>> SELECT.format(cols=', '.join(['cat', 'area']), tname='table')
'SELECT cat, area FROM table;'
>>> SELECT_WHERE.format(cols=', '.join(['cat', 'area']),
... tname='table', condition='area>10000')
'SELECT cat, area FROM table WHERE area>10000;'
pygrass.vector.table module¶
Created on Wed Aug 8 15:29:21 2012
@author: pietro
-
class
pygrass.vector.table.
Columns
(tname, connection, key='cat')[source]¶ Bases:
object
Object to work with columns table.
It is possible to instantiate a Columns object given the table name and the database connection.
For a sqlite table:
>>> import sqlite3 >>> path = '$GISDBASE/$LOCATION_NAME/$MAPSET/sqlite/sqlite.db' >>> cols_sqlite = Columns(test_vector_name, ... sqlite3.connect(get_path(path))) >>> cols_sqlite.tname 'table_doctest_map'
For a postgreSQL table:
>>> import psycopg2 as pg #doctest: +SKIP >>> cols_pg = Columns(test_vector_name, ... pg.connect('host=localhost dbname=grassdb')) #doctest: +SKIP >>> cols_pg.tname #doctest: +SKIP 'table_doctest_map' #doctest: +SKIP
-
add
(col_name, col_type)[source]¶ Add a new column to the table.
Parameters: - col_name (str) – the name of column to add
- col_type (str) – the tipe of column to add
>>> import sqlite3 >>> path = '$GISDBASE/$LOCATION_NAME/$MAPSET/sqlite/sqlite.db' >>> from grass.pygrass.utils import copy, remove >>> copy(test_vector_name,'mycensus','vect') >>> cols_sqlite = Columns('mycensus', ... sqlite3.connect(get_path(path))) >>> cols_sqlite.add(['n_pizza'], ['INT']) >>> 'n_pizza' in cols_sqlite True >>> import psycopg2 as pg # doctest: +SKIP >>> cols_pg = Columns('boundary_municp_pg', ... pg.connect('host=localhost dbname=grassdb')) #doctest: +SKIP >>> cols_pg.add('n_pizza', 'INT') # doctest: +SKIP >>> 'n_pizza' in cols_pg # doctest: +SKIP True >>> remove('mycensus', 'vect')
-
cast
(col_name, new_type)[source]¶ Change the column type.
Parameters: - col_name (str) – the name of column
- new_type (str) – the new type of column
>>> import sqlite3 >>> path = '$GISDBASE/$LOCATION_NAME/$MAPSET/sqlite/sqlite.db' >>> from grass.pygrass.utils import copy, remove >>> copy(test_vector_name,'mycensus','vect') >>> cols_sqlite = Columns('mycensus', ... sqlite3.connect(get_path(path))) >>> cols_sqlite.add(['n_pizzas'], ['INT']) >>> cols_sqlite.cast('n_pizzas', 'float8') # doctest: +ELLIPSIS Traceback (most recent call last): ... grass.exceptions.DBError: SQLite does not support to cast columns. >>> import psycopg2 as pg # doctest: +SKIP >>> cols_pg = Columns(test_vector_name, ... pg.connect('host=localhost dbname=grassdb')) # doctest: +SKIP >>> cols_pg.cast('n_pizzas', 'float8') # doctest: +SKIP >>> cols_pg['n_pizzas'] # doctest: +SKIP 'float8' >>> remove('mycensus', 'vect')
Warning
It is not possible to cast a column with sqlite
-
drop
(col_name)[source]¶ Drop a column from the table.
Parameters: col_name (str) – the name of column to remove >>> import sqlite3 >>> path = '$GISDBASE/$LOCATION_NAME/$MAPSET/sqlite/sqlite.db' >>> from grass.pygrass.utils import copy, remove >>> copy(test_vector_name,'mycensus','vect') >>> cols_sqlite = Columns('mycensus', ... sqlite3.connect(get_path(path))) >>> cols_sqlite.drop('name') # doctest: +ELLIPSIS >>> 'name' in cols_sqlite False
>>> import psycopg2 as pg # doctest: +SKIP >>> cols_pg = Columns(test_vector_name, ... pg.connect('host=localhost dbname=grassdb')) # doctest: +SKIP >>> cols_pg.drop('name') # doctest: +SKIP >>> 'name' in cols_pg # doctest: +SKIP False >>> remove('mycensus','vect')
-
is_pg
()[source]¶ Return True if is a psycopg connection.
>>> import sqlite3 >>> path = '$GISDBASE/$LOCATION_NAME/$MAPSET/sqlite/sqlite.db' >>> cols_sqlite = Columns(test_vector_name, ... sqlite3.connect(get_path(path))) >>> cols_sqlite.is_pg() False >>> import psycopg2 as pg #doctest: +SKIP >>> cols_pg = Columns(test_vector_name, ... pg.connect('host=localhost dbname=grassdb')) #doctest: +SKIP >>> cols_pg.is_pg() #doctest: +SKIP True
-
items
()[source]¶ Return a list of tuple with column name and column type.
>>> import sqlite3 >>> path = '$GISDBASE/$LOCATION_NAME/$MAPSET/sqlite/sqlite.db' >>> cols_sqlite = Columns(test_vector_name, ... sqlite3.connect(get_path(path))) >>> cols_sqlite.items() # doctest: +ELLIPSIS [('cat', 'INTEGER'), ('name', 'varchar(50)'), ('value', 'double precision')] >>> import psycopg2 as pg # doctest: +SKIP >>> cols_pg = Columns(test_vector_name, ... pg.connect('host=localhost dbname=grassdb')) # doctest: +SKIP >>> cols_pg.items() # doctest: +ELLIPSIS +SKIP [('cat', 'INTEGER'), ('name', 'varchar(50)'), ('value', 'double precision')]
-
names
(remove=None, unicod=True)[source]¶ Return a list with the column names. Remove it is used to remove a columns.
>>> import sqlite3 >>> path = '$GISDBASE/$LOCATION_NAME/$MAPSET/sqlite/sqlite.db' >>> cols_sqlite = Columns(test_vector_name, ... sqlite3.connect(get_path(path))) >>> cols_sqlite.names() # doctest: +ELLIPSIS ['cat', 'name', 'value'] >>> import psycopg2 as pg # doctest: +SKIP >>> cols_pg = Columns(test_vector_name, # doctest: +SKIP ... pg.connect('host=localhost dbname=grassdb')) >>> cols_pg.names() # doctest: +ELLIPSIS +SKIP ['cat', 'name', 'value']
-
rename
(old_name, new_name)[source]¶ Rename a column of the table.
Parameters: - old_name (str) – the name of existing column
- new_name (str) – the name of new column
>>> import sqlite3 >>> path = '$GISDBASE/$LOCATION_NAME/$MAPSET/sqlite/sqlite.db' >>> from grass.pygrass.utils import copy, remove >>> copy(test_vector_name,'mycensus','vect') >>> cols_sqlite = Columns('mycensus', ... sqlite3.connect(get_path(path))) >>> cols_sqlite.add(['n_pizza'], ['INT']) >>> 'n_pizza' in cols_sqlite True >>> cols_sqlite.rename('n_pizza', 'n_pizzas') # doctest: +ELLIPSIS >>> 'n_pizza' in cols_sqlite False >>> 'n_pizzas' in cols_sqlite True
>>> import psycopg2 as pg # doctest: +SKIP >>> cols_pg = Columns(test_vector_name, ... pg.connect('host=localhost dbname=grassdb')) # doctest: +SKIP >>> cols_pg.rename('n_pizza', 'n_pizzas') # doctest: +SKIP >>> 'n_pizza' in cols_pg # doctest: +SKIP False >>> 'n_pizzas' in cols_pg # doctest: +SKIP True >>> remove('mycensus', 'vect')
-
sql_descr
(remove=None)[source]¶ Return a string with description of columns. Remove it is used to remove a columns.
>>> import sqlite3 >>> path = '$GISDBASE/$LOCATION_NAME/$MAPSET/sqlite/sqlite.db' >>> cols_sqlite = Columns(test_vector_name, ... sqlite3.connect(get_path(path))) >>> cols_sqlite.sql_descr() # doctest: +ELLIPSIS 'cat INTEGER, name varchar(50), value double precision' >>> import psycopg2 as pg # doctest: +SKIP >>> cols_pg = Columns(test_vector_name, ... pg.connect('host=localhost dbname=grassdb')) # doctest: +SKIP >>> cols_pg.sql_descr() # doctest: +ELLIPSIS +SKIP 'cat INTEGER, name varchar(50), value double precision'
-
types
()[source]¶ Return a list with the column types.
>>> import sqlite3 >>> path = '$GISDBASE/$LOCATION_NAME/$MAPSET/sqlite/sqlite.db' >>> cols_sqlite = Columns(test_vector_name, ... sqlite3.connect(get_path(path))) >>> cols_sqlite.types() # doctest: +ELLIPSIS ['INTEGER', 'varchar(50)', 'double precision'] >>> import psycopg2 as pg # doctest: +SKIP >>> cols_pg = Columns(test_vector_name, ... pg.connect('host=localhost dbname=grassdb')) # doctest: +SKIP >>> cols_pg.types() # doctest: +ELLIPSIS +SKIP ['INTEGER', 'varchar(50)', 'double precision']
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class
pygrass.vector.table.
DBlinks
(c_mapinfo)[source]¶ Bases:
object
Interface containing link to the table DB.
>>> from grass.pygrass.vector import VectorTopo >>> cens = VectorTopo(test_vector_name) >>> cens.open(mode='r') >>> dblinks = DBlinks(cens.c_mapinfo) >>> dblinks DBlinks([Link(1, table_doctest_map, sqlite)]) >>> dblinks[0] Link(1, table_doctest_map, sqlite) >>> dblinks[test_vector_name] Link(1, table_doctest_map, sqlite) >>> cens.close()
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add
(link)[source]¶ Add a new link. Need to open vector map in write mode
Parameters: link – the Link to add to the DBlinks
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by_index
(indx)[source]¶ Return a Link object by index
Parameters: indx (int) – the index where add new point
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by_layer
(layer)[source]¶ Return the chosen Link using the layer
Parameters: layer (int) – the number of layer
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by_name
(name)[source]¶ Return the chosen Link using the name
Parameters: name (str) – the name of Link
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remove
(key, force=False)[source]¶ Remove a link. If force set to true remove also the table
Parameters: - key (str) – the key of Link
- force (boole) – if True remove also the table from database otherwise only the link between table and vector
>>> from grass.pygrass.vector import VectorTopo >>> test_vect = VectorTopo(test_vector_name) >>> test_vect.open(mode='r') >>> dblinks = DBlinks(test_vect.c_mapinfo) >>> dblinks DBlinks([Link(1, table_doctest_map, sqlite)]) >>> dblinks.remove('pg_link') # doctest: +SKIP >>> dblinks # need to open vector map in write mode DBlinks([Link(1, table_doctest_map, sqlite)])
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class
pygrass.vector.table.
Filters
(tname)[source]¶ Bases:
object
Help user to build a simple sql query.
>>> filter = Filters('table') >>> filter.get_sql() 'SELECT * FROM table;' >>> filter.where("area<10000").get_sql() 'SELECT * FROM table WHERE area<10000;' >>> filter.select("cat", "area").get_sql() 'SELECT cat, area FROM table WHERE area<10000;' >>> filter.order_by("area").limit(10).get_sql() 'SELECT cat, area FROM table WHERE area<10000 ORDER BY area LIMIT 10;'
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group_by
(*groupby)[source]¶ Create the group by condition
Parameters: groupby (str, list) – the name of column/s to group the result
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limit
(number)[source]¶ Create the limit condition
Parameters: number (int) – the number to limit the result
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class
pygrass.vector.table.
Link
(layer=1, name=None, table=None, key='cat', database='$GISDBASE/$LOCATION_NAME/$MAPSET/sqlite/sqlite.db', driver='sqlite', c_fieldinfo=None)[source]¶ Bases:
object
Define a Link between vector map and the attributes table.
It is possible to define a Link object or given all the information (layer, name, table name, key, database, driver):
>>> link = Link(1, 'link0', test_vector_name, 'cat', ... '$GISDBASE/$LOCATION_NAME/$MAPSET/sqlite/sqlite.db', 'sqlite') >>> link.layer 1 >>> link.name 'link0' >>> link.table_name 'table_doctest_map' >>> link.key 'cat' >>> link.database '$GISDBASE/$LOCATION_NAME/$MAPSET/sqlite/sqlite.db' >>> link.driver 'sqlite' >>> link Link(1, link0, sqlite)
It is possible to change parameters with:
>>> link.driver = 'pg' # doctest: +SKIP >>> link.driver # doctest: +SKIP 'pg' >>> link.driver = 'postgres' # doctest: +ELLIPSIS +SKIP Traceback (most recent call last): ... TypeError: Driver not supported, use: sqlite, pg. >>> link.driver # doctest: +SKIP 'pg' >>> link.number = 0 # doctest: +ELLIPSIS +SKIP Traceback (most recent call last): ... TypeError: Number must be positive and greater than 0.
Or given a c_fieldinfo object that is a ctypes pointer to the field_info C struct.
>>> link = Link(c_fieldinfo = ctypes.pointer(libvect.field_info()))
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connection
()[source]¶ Return a connection object.
>>> link = Link(1, 'link0', test_vector_name, 'cat', ... '$GISDBASE/$LOCATION_NAME/$MAPSET/sqlite/sqlite.db', ... 'sqlite') >>> conn = link.connection() >>> cur = conn.cursor() >>> link.table_name 'table_doctest_map' >>> cur.execute("SELECT cat, name, value from %s" % ... link.table_name) # doctest: +ELLIPSIS <sqlite3.Cursor object at ...> >>> cur.fetchone() #doctest: +ELLIPSIS +NORMALIZE_WHITESPACE (1, 'point', 1.0) >>> cur.close() >>> conn.close()
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database
¶ Set and obtain database value
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driver
¶ Set and obtain driver value. The drivers supported by PyGRASS are: SQLite and PostgreSQL
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info
()[source]¶ Print information of the link.
>>> link = Link(1, 'link0', test_vector_name, 'cat', ... '$GISDBASE/$LOCATION_NAME/$MAPSET/sqlite/sqlite.db', ... 'sqlite') >>> link.info() layer: 1 name: link0 table: table_doctest_map key: cat database: $GISDBASE/$LOCATION_NAME/$MAPSET/sqlite/sqlite.db driver: sqlite
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key
¶ Set and obtain cat value
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layer
¶ Set and obtain layer number
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name
¶ Set and obtain name vale
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table
()[source]¶ Return a Table object.
>>> link = Link(1, 'link0', test_vector_name, 'cat', ... '$GISDBASE/$LOCATION_NAME/$MAPSET/sqlite/sqlite.db', ... 'sqlite') >>> table = link.table() >>> table.filters.select('cat', 'name', 'value') Filters('SELECT cat, name, value FROM table_doctest_map;') >>> cur = table.execute() >>> cur.fetchone() (1, 'point', 1.0) >>> cur.close()
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table_name
¶ Set and obtain table name value
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class
pygrass.vector.table.
Table
(name, connection, key='cat')[source]¶ Bases:
object
>>> import sqlite3 >>> path = '$GISDBASE/$LOCATION_NAME/PERMANENT/sqlite/sqlite.db' >>> tab_sqlite = Table(name=test_vector_name, ... connection=sqlite3.connect(get_path(path))) >>> tab_sqlite.name 'table_doctest_map' >>> import psycopg2 # doctest: +SKIP >>> tab_pg = Table(test_vector_name, ... psycopg2.connect('host=localhost dbname=grassdb', ... 'pg')) # doctest: +SKIP >>> tab_pg.columns # doctest: +ELLIPSIS +SKIP Columns([('cat', 'int4'), ...])
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create
(cols, name=None, overwrite=False, cursor=None)[source]¶ Create a new table
Parameters: - cols –
- name (str) – the name of table to create, None for the name of Table object
- overwrite (bool) – overwrite existing table
- cursor (Cursor object) – the cursor to connect, if None it use the cursor of connection table object
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drop
(cursor=None, force=False)[source]¶ Method to drop table from database
Parameters: - cursor (Cursor object) – the cursor to connect, if None it use the cursor of connection table object
- force (bool) – True to remove the table, by default False to print advice
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execute
(sql_code=None, cursor=None, many=False, values=None)[source]¶ Execute SQL code from a given string or build with filters and return a cursor object.
Parameters: - sql_code (str) – the SQL code to execute, if not pass it use filters variable
- cursor (Cursor object) – the cursor to connect, if None it use the cursor of connection table object
- many (bool) – True to run executemany function
- values (list of tuple) – The values to substitute into sql_code string
>>> import sqlite3 >>> path = '$GISDBASE/$LOCATION_NAME/$MAPSET/sqlite/sqlite.db' >>> tab_sqlite = Table(name=test_vector_name, ... connection=sqlite3.connect(get_path(path))) >>> tab_sqlite.filters.select('cat', 'name').order_by('value') Filters('SELECT cat, name FROM table_doctest_map ORDER BY value;') >>> cur = tab_sqlite.execute() >>> cur.fetchone() #doctest: +ELLIPSIS +NORMALIZE_WHITESPACE (1, 'point')
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exist
(cursor=None)[source]¶ Return True if the table already exist in the DB, False otherwise
Parameters: cursor – the cursor to connect, if None it use the cursor of connection table object
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insert
(values, cursor=None, many=False)[source]¶ Insert a new row
Parameters: - values (tuple) – a tuple of values to insert, it is possible to insert more rows using a list of tuple and parameter many
- cursor (Cursor object) – the cursor to connect, if None it use the cursor of connection table object
- many (bool) – True to run executemany function
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n_rows
()[source]¶ Return the number of rows
>>> import sqlite3 >>> path = '$GISDBASE/$LOCATION_NAME/$MAPSET/sqlite/sqlite.db' >>> tab_sqlite = Table(name=test_vector_name, ... connection=sqlite3.connect(get_path(path))) >>> tab_sqlite.n_rows() 3
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name
¶ Set and obtain table name
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update
(key, values, cursor=None)[source]¶ Update a table row
Parameters: - key (int) – the rowid
- values (list) – the values to insert without row id. For example if we have a table with four columns: cat, c0, c1, c2 the values list should containing only c0, c1, c2 values.
- cursor (Cursor object) – the cursor to connect, if None it use the cursor of connection table object
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pygrass.vector.table.
get_path
(path, vect_name=None)[source]¶ Return the full path to the database; replacing environment variable with real values
Parameters: - path – The path with substitutional parameter
- vect_name – The name of the vector map
>>> from grass.script.core import gisenv >>> import os >>> path = '$GISDBASE/$LOCATION_NAME/$MAPSET/sqlite/sqlite.db' >>> new_path = get_path(path) >>> new_path2 = os.path.join(gisenv()['GISDBASE'], gisenv()['LOCATION_NAME'], ... gisenv()['MAPSET'], 'sqlite', 'sqlite.db') >>> new_path.replace("//","/") == new_path2.replace("//","/") True >>> path = '$GISDBASE/$LOCATION_NAME/$MAPSET/vector/$MAP/sqlite.db' >>> new_path = get_path(path, "test") >>> new_path2 = os.path.join(gisenv()['GISDBASE'], gisenv()['LOCATION_NAME'], ... gisenv()['MAPSET'], 'vector', 'test', 'sqlite.db') >>> new_path.replace("//","/") == new_path2.replace("//","/") True
Module contents¶
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class
pygrass.vector.
Vector
(name, mapset='', *args, **kwargs)[source]¶ Bases:
grass.pygrass.vector.abstract.Info
Vector class is the grass vector format without topology
>>> from grass.pygrass.vector import Vector >>> test_vect = Vector(test_vector_name) >>> test_vect.is_open() False >>> test_vect.mapset '' >>> test_vect.exist() True >>> test_vect.overwrite False
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has_color_table
()[source]¶ Return if vector has color table associated in file system; Color table stored in the vector’s attribute table well be not checked
>>> test_vect = Vector(test_vector_name) >>> test_vect.open(mode='r') >>> test_vect.has_color_table() False
>>> test_vect.close() >>> from grass.pygrass.utils import copy, remove >>> copy(test_vector_name,'mytest_vect','vect') >>> from grass.pygrass.modules.shortcuts import vector as v >>> v.colors(map='mytest_vect', color='population', column='value') Module('v.colors') >>> mytest_vect = Vector('mytest_vect') >>> mytest_vect.open(mode='r') >>> mytest_vect.has_color_table() True >>> mytest_vect.close() >>> remove('mytest_vect', 'vect')
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write
(geo_obj, cat=None, attrs=None)[source]¶ Write geometry features and attributes.
Parameters: - geo_obj (geometry GRASS object) – a geometry grass object define in grass.pygrass.vector.geometry
- attrs (list) – a list with the values that will be insert in the attribute table.
- cat (integer) – The category of the geometry feature, otherwise the c_cats attribute of the geometry object will be used.
Open a new vector map
>>> new = VectorTopo('newvect') >>> new.exist() False
define the new columns of the attribute table
>>> cols = [(u'cat', 'INTEGER PRIMARY KEY'), ... (u'name', 'TEXT')]
open the vector map in write mode
>>> new.open('w', tab_name='newvect', tab_cols=cols)
import a geometry feature
>>> from grass.pygrass.vector.geometry import Point
create two points
>>> point0 = Point(0, 0) >>> point1 = Point(1, 1)
then write the two points on the map, with
>>> new.write(point0, cat=1, attrs=('pub',)) >>> new.write(point1, cat=2, attrs=('resturant',))
commit the db changes
>>> new.table.conn.commit() >>> new.table.execute().fetchall() [(1, 'pub'), (2, 'resturant')]
close the vector map
>>> new.close() >>> new.exist() True
then play with the map
>>> new.open(mode='r') >>> new.read(1) Point(0.000000, 0.000000) >>> new.read(2) Point(1.000000, 1.000000) >>> new.read(1).attrs['name'] 'pub' >>> new.read(2).attrs['name'] 'resturant' >>> new.close() >>> new.remove()
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class
pygrass.vector.
VectorTopo
(name, mapset='', *args, **kwargs)[source]¶ Bases:
pygrass.vector.Vector
Vector class with the support of the GRASS topology.
Open a vector map using the with statement:
>>> with VectorTopo(test_vector_name, mode='r') as test_vect: ... for feature in test_vect[:7]: ... print(feature.attrs['name']) ... point point point line line line >>> test_vect.is_open() False
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areas_to_wkb_list
(bbox=None, field=1)[source]¶ Return all features of type point, line, boundary or centroid as a list of Well Known Binary representations (WKB) (id, cat, wkb) triplets located in a specific bounding box.
Parameters: - bbox (grass.pygrass.vector.basic.Bbox) – The boundingbox to search for features, if bbox=None the boundingbox of the whole vector map layer is used
- field (integer) – The centroid category field
Returns: A list of triplets, or None if nothing was found
The well known binary are stored in byte arrays.
Examples:
>>> from grass.pygrass.vector import VectorTopo >>> from grass.pygrass.vector.basic import Bbox >>> test_vect = VectorTopo(test_vector_name) >>> test_vect.open('r')
>>> bbox = Bbox(north=20, south=-1, east=20, west=-1) >>> result = test_vect.areas_to_wkb_list(bbox=bbox) >>> len(result) 4 >>> for entry in result: ... a_id, cat, wkb = entry ... print((a_id, cat, len(wkb))) (1, 3, 225) (2, 3, 141) (3, 3, 93) (4, 3, 141)
>>> result = test_vect.areas_to_wkb_list() >>> len(result) 4 >>> for entry in result: ... a_id, cat, wkb = entry ... print((a_id, cat, len(wkb))) (1, 3, 225) (2, 3, 141) (3, 3, 93) (4, 3, 141)
>>> test_vect.close()
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cat
(cat_id, vtype, layer=None, generator=False, geo=None)[source]¶ Return the geometry features with category == cat_id.
Parameters: - cat_id (int) – the category number
- vtype (str) – the type of geometry feature that we are looking for
- layer (int) – the layer number that will be used
- generator (bool) – if True return a generator otherwise it return a list of features
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close
(build=True, release=True)[source]¶ Close the VectorTopo map, if release is True, the memory occupied by spatial index is released
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delete
(feature_id)[source]¶ Remove a feature by its id
Parameters: feature_id (int) – the id of the feature
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features_to_wkb_list
(bbox=None, feature_type='point', field=1)[source]¶ Return all features of type point, line, boundary or centroid as a list of Well Known Binary representations (WKB) (id, cat, wkb) triplets located in a specific bounding box.
Parameters: - bbox (grass.pygrass.vector.basic.Bbox) – The boundingbox to search for features, if bbox=None the boundingbox of the whole vector map layer is used
- feature_type –
- The type of feature that should be converted to
- the Well Known Binary (WKB) format. Supported are:
’point’ -> libvect.GV_POINT 1 ‘line’ -> libvect.GV_LINE 2 ‘boundary’ -> libvect.GV_BOUNDARY 3 ‘centroid’ -> libvect.GV_CENTROID 4
- field (integer) – The category field
Returns: A list of triplets, or None if nothing was found
The well known binary are stored in byte arrays.
Examples:
>>> from grass.pygrass.vector import VectorTopo >>> from grass.pygrass.vector.basic import Bbox >>> test_vect = VectorTopo(test_vector_name) >>> test_vect.open('r')
>>> bbox = Bbox(north=20, south=-1, east=20, west=-1) >>> result = test_vect.features_to_wkb_list(bbox=bbox, ... feature_type="point") >>> len(result) 3 >>> for entry in result: ... f_id, cat, wkb = entry ... print((f_id, cat, len(wkb))) (1, 1, 21) (2, 1, 21) (3, 1, 21)
>>> result = test_vect.features_to_wkb_list(bbox=None, ... feature_type="line") >>> len(result) 3 >>> for entry in result: ... f_id, cat, wkb = entry ... print((f_id, cat, len(wkb))) (4, 2, 57) (5, 2, 57) (6, 2, 57)
>>> result = test_vect.features_to_wkb_list(bbox=bbox, ... feature_type="boundary") >>> len(result) 11
>>> result = test_vect.features_to_wkb_list(bbox=None, ... feature_type="centroid") >>> len(result) 4
>>> for entry in result: ... f_id, cat, wkb = entry ... print((f_id, cat, len(wkb))) (19, 3, 21) (18, 3, 21) (20, 3, 21) (21, 3, 21)
>>> result = test_vect.features_to_wkb_list(bbox=bbox, ... feature_type="blub") Traceback (most recent call last): ... grass.exceptions.GrassError: Unsupported feature type <blub>, supported are <point,line,boundary,centroid>
>>> test_vect.close()
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num_primitive_of
(primitive)[source]¶ Return the number of primitive
Parameters: primitive (str) – the name of primitive to query; the supported values are:
- boundary,
- centroid,
- face,
- kernel,
- line,
- point
- area
- volume
>>> test_vect = VectorTopo(test_vector_name) >>> test_vect.open(mode='r') >>> test_vect.num_primitive_of('point') 3 >>> test_vect.num_primitive_of('line') 3 >>> test_vect.num_primitive_of('centroid') 4 >>> test_vect.num_primitive_of('boundary') 11 >>> test_vect.close()
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number_of
(vtype)[source]¶ Return the number of the chosen element type
Parameters: vtype – the name of type to query; the supported values are: areas, dblinks, faces, holes, islands, kernels, points, lines, centroids, boundaries, nodes, line_points, update_lines, update_nodes, volumes
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read
(feature_id)[source]¶ Return a geometry object given the feature id.
Parameters: feature_id (int) – the id of feature to obtain >>> test_vect = VectorTopo(test_vector_name) >>> test_vect.open(mode='r') >>> feature1 = test_vect.read(0) #doctest: +ELLIPSIS Traceback (most recent call last): ... ValueError: The index must be >0, 0 given. >>> feature1 = test_vect.read(5) >>> feature1 Line([Point(12.000000, 4.000000), Point(12.000000, 2.000000), Point(12.000000, 0.000000)]) >>> feature1.length() 4.0 >>> test_vect.read(-1) Centroid(7.500000, 3.500000) >>> len(test_vect) 21 >>> test_vect.read(21) Centroid(7.500000, 3.500000) >>> test_vect.read(22) #doctest: +ELLIPSIS Traceback (most recent call last): ... IndexError: Index out of range >>> test_vect.close()
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rewind
()[source]¶ Rewind vector map to cause reads to start at beginning.
>>> test_vect = VectorTopo(test_vector_name) >>> test_vect.open(mode='r') >>> test_vect.next() Point(10.000000, 6.000000) >>> test_vect.next() Point(12.000000, 6.000000) >>> test_vect.next() Point(14.000000, 6.000000) >>> test_vect.rewind() >>> test_vect.next() Point(10.000000, 6.000000) >>> test_vect.close()
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rewrite
(geo_obj, cat, attrs=None, **kargs)[source]¶ Rewrite a geometry features
>>> cols = [(u'cat', 'INTEGER PRIMARY KEY'), ... (u'name', 'TEXT')]
Generate a new vector map
>>> test_vect = VectorTopo('newvect_2') >>> test_vect.open('w', tab_name='newvect_2', tab_cols=cols, ... overwrite=True)
import a geometry feature
>>> from grass.pygrass.vector.geometry import Point
create two points
>>> point0 = Point(0, 0) >>> point1 = Point(1, 1) >>> point2 = Point(2, 2)
then write the two points on the map, with
>>> test_vect.write(point0, cat=1, attrs=('pub',)) >>> test_vect.write(point1, cat=2, attrs=('resturant',)) >>> test_vect.table.conn.commit() # save changes in the DB >>> test_vect.table_to_dict() {1: [1, 'pub'], 2: [2, 'resturant']} >>> test_vect.close()
Now rewrite one point of the vector map:
>>> test_vect.open('rw') >>> test_vect.rewrite(point2, cat=1, attrs=('Irish Pub',)) >>> test_vect.table.conn.commit() # save changes in the DB >>> test_vect.close()
Check the output:
>>> test_vect.open('r') >>> test_vect[1] == point2 True >>> test_vect[1].attrs['name'] == 'Irish Pub' True >>> test_vect.close() >>> test_vect.remove()
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table_to_dict
(where=None)[source]¶ Return the attribute table as a dictionary with the category as keys
The columns have the order of the self.table.columns.names() list.
Examples
>>> from grass.pygrass.vector import VectorTopo >>> from grass.pygrass.vector.basic import Bbox >>> test_vect = VectorTopo(test_vector_name) >>> test_vect.open('r')
>>> test_vect.table_to_dict() {1: [1, 'point', 1.0], 2: [2, 'line', 2.0], 3: [3, 'centroid', 3.0]}
>>> test_vect.table_to_dict(where="value > 2") {3: [3, 'centroid', 3.0]}
>>> test_vect.table_to_dict(where="value > 0") {1: [1, 'point', 1.0], 2: [2, 'line', 2.0], 3: [3, 'centroid', 3.0]}
>>> test_vect.table.filters.get_sql() 'SELECT cat,name,value FROM vector_doctest_map WHERE value > 0 ORDER BY cat;'
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viter
(vtype, idonly=False)[source]¶ Return an iterator of vector features
Parameters: - vtype (str) – the name of type to query; the supported values are: areas, dblinks, faces, holes, islands, kernels, line_points, lines, nodes, points, update_lines, update_nodes, volumes
- idonly – variable to return only the id of features instead of full features
to sort the result in a efficient way, use:
>>> from operator import methodcaller as method >>> areas.sort(key=method('area'), reverse=True) # sort the list >>> for area in areas[:3]: ... print(area, area.area()) Area(1) 12.0 Area(2) 8.0 Area(4) 8.0 >>> areas = [area for area in test_vect.viter('areas')] >>> for area in areas: ... print(area.centroid().cat) 3 3 3 3 >>> test_vect.close()
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