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shapefile.py
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shapefile.py
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"""
shapefile.py
Provides read and write support for ESRI Shapefiles.
author: jlawhead<at>geospatialpython.com
version: 2.1.3
Compatible with Python versions 2.7-3.x
"""
__version__ = "2.1.3"
from struct import pack, unpack, calcsize, error, Struct
import os
import sys
import time
import array
import tempfile
import warnings
import io
from datetime import date
# Constants for shape types
NULL = 0
POINT = 1
POLYLINE = 3
POLYGON = 5
MULTIPOINT = 8
POINTZ = 11
POLYLINEZ = 13
POLYGONZ = 15
MULTIPOINTZ = 18
POINTM = 21
POLYLINEM = 23
POLYGONM = 25
MULTIPOINTM = 28
MULTIPATCH = 31
SHAPETYPE_LOOKUP = {
0: 'NULL',
1: 'POINT',
3: 'POLYLINE',
5: 'POLYGON',
8: 'MULTIPOINT',
11: 'POINTZ',
13: 'POLYLINEZ',
15: 'POLYGONZ',
18: 'MULTIPOINTZ',
21: 'POINTM',
23: 'POLYLINEM',
25: 'POLYGONM',
28: 'MULTIPOINTM',
31: 'MULTIPATCH'}
TRIANGLE_STRIP = 0
TRIANGLE_FAN = 1
OUTER_RING = 2
INNER_RING = 3
FIRST_RING = 4
RING = 5
PARTTYPE_LOOKUP = {
0: 'TRIANGLE_STRIP',
1: 'TRIANGLE_FAN',
2: 'OUTER_RING',
3: 'INNER_RING',
4: 'FIRST_RING',
5: 'RING'}
# Python 2-3 handling
PYTHON3 = sys.version_info[0] == 3
if PYTHON3:
xrange = range
izip = zip
else:
from itertools import izip
# Helpers
MISSING = [None,'']
NODATA = -10e38 # as per the ESRI shapefile spec, only used for m-values.
if PYTHON3:
def b(v, encoding='utf-8', encodingErrors='strict'):
if isinstance(v, str):
# For python 3 encode str to bytes.
return v.encode(encoding, encodingErrors)
elif isinstance(v, bytes):
# Already bytes.
return v
elif v is None:
# Since we're dealing with text, interpret None as ""
return b""
else:
# Force string representation.
return str(v).encode(encoding, encodingErrors)
def u(v, encoding='utf-8', encodingErrors='strict'):
if isinstance(v, bytes):
# For python 3 decode bytes to str.
return v.decode(encoding, encodingErrors)
elif isinstance(v, str):
# Already str.
return v
elif v is None:
# Since we're dealing with text, interpret None as ""
return ""
else:
# Force string representation.
return bytes(v).decode(encoding, encodingErrors)
def is_string(v):
return isinstance(v, str)
else:
def b(v, encoding='utf-8', encodingErrors='strict'):
if isinstance(v, unicode):
# For python 2 encode unicode to bytes.
return v.encode(encoding, encodingErrors)
elif isinstance(v, bytes):
# Already bytes.
return v
elif v is None:
# Since we're dealing with text, interpret None as ""
return ""
else:
# Force string representation.
return unicode(v).encode(encoding, encodingErrors)
def u(v, encoding='utf-8', encodingErrors='strict'):
if isinstance(v, bytes):
# For python 2 decode bytes to unicode.
return v.decode(encoding, encodingErrors)
elif isinstance(v, unicode):
# Already unicode.
return v
elif v is None:
# Since we're dealing with text, interpret None as ""
return u""
else:
# Force string representation.
return bytes(v).decode(encoding, encodingErrors)
def is_string(v):
return isinstance(v, basestring)
# Begin
class _Array(array.array):
"""Converts python tuples to lists of the appropritate type.
Used to unpack different shapefile header parts."""
def __repr__(self):
return str(self.tolist())
def signed_area(coords):
"""Return the signed area enclosed by a ring using the linear time
algorithm. A value >= 0 indicates a counter-clockwise oriented ring.
"""
xs, ys = map(list, list(zip(*coords))[:2]) # ignore any z or m values
xs.append(xs[1])
ys.append(ys[1])
return sum(xs[i]*(ys[i+1]-ys[i-1]) for i in range(1, len(coords)))/2.0
def ring_bbox(coords):
"""Calculates and returns the bounding box of a ring.
"""
xs,ys = zip(*coords)
bbox = min(xs),min(ys),max(xs),max(ys)
return bbox
def bbox_overlap(bbox1, bbox2):
"""Tests whether two bounding boxes overlap, returning a boolean
"""
xmin1,ymin1,xmax1,ymax1 = bbox1
xmin2,ymin2,xmax2,ymax2 = bbox2
overlap = (xmin1 <= xmax2 and xmax1 >= xmin2 and ymin1 <= ymax2 and ymax1 >= ymin2)
return overlap
def bbox_contains(bbox1, bbox2):
"""Tests whether bbox1 fully contains bbox2, returning a boolean
"""
xmin1,ymin1,xmax1,ymax1 = bbox1
xmin2,ymin2,xmax2,ymax2 = bbox2
contains = (xmin1 < xmin2 and xmax1 > xmax2 and ymin1 < ymin2 and ymax1 > ymax2)
return contains
def ring_contains_point(coords, p):
"""Fast point-in-polygon crossings algorithm, MacMartin optimization.
Adapted from code by Eric Haynes
http://www.realtimerendering.com/resources/GraphicsGems//gemsiv/ptpoly_haines/ptinpoly.c
Original description:
Shoot a test ray along +X axis. The strategy, from MacMartin, is to
compare vertex Y values to the testing point's Y and quickly discard
edges which are entirely to one side of the test ray.
"""
tx,ty = p
# get initial test bit for above/below X axis
vtx0 = coords[0]
yflag0 = ( vtx0[1] >= ty )
inside_flag = False
for vtx1 in coords[1:]:
yflag1 = ( vtx1[1] >= ty )
# check if endpoints straddle (are on opposite sides) of X axis
# (i.e. the Y's differ); if so, +X ray could intersect this edge.
if yflag0 != yflag1:
xflag0 = ( vtx0[0] >= tx )
# check if endpoints are on same side of the Y axis (i.e. X's
# are the same); if so, it's easy to test if edge hits or misses.
if xflag0 == ( vtx1[0] >= tx ):
# if edge's X values both right of the point, must hit
if xflag0:
inside_flag = not inside_flag
else:
# compute intersection of pgon segment with +X ray, note
# if >= point's X; if so, the ray hits it.
if ( vtx1[0] - (vtx1[1]-ty) * ( vtx0[0]-vtx1[0]) / (vtx0[1]-vtx1[1]) ) >= tx:
inside_flag = not inside_flag
# move to next pair of vertices, retaining info as possible
yflag0 = yflag1
vtx0 = vtx1
return inside_flag
def ring_sample(coords, ccw=False):
"""Return a sample point guaranteed to be within a ring, by efficiently
finding the first centroid of a coordinate triplet whose orientation
matches the orientation of the ring and passes the point-in-ring test.
The orientation of the ring is assumed to be clockwise, unless ccw
(counter-clockwise) is set to True.
"""
triplet = []
def itercoords():
# iterate full closed ring
for p in coords:
yield p
# finally, yield the second coordinate to the end to allow checking the last triplet
yield coords[1]
for p in itercoords():
# add point to triplet (but not if duplicate)
if p not in triplet:
triplet.append(p)
# new triplet, try to get sample
if len(triplet) == 3:
# check that triplet does not form a straight line (not a triangle)
is_straight_line = (triplet[0][1] - triplet[1][1]) * (triplet[0][0] - triplet[2][0]) == (triplet[0][1] - triplet[2][1]) * (triplet[0][0] - triplet[1][0])
if not is_straight_line:
# get triplet orientation
closed_triplet = triplet + [triplet[0]]
triplet_ccw = signed_area(closed_triplet) >= 0
# check that triplet has the same orientation as the ring (means triangle is inside the ring)
if ccw == triplet_ccw:
# get triplet centroid
xs,ys = zip(*triplet)
xmean,ymean = sum(xs) / 3.0, sum(ys) / 3.0
# check that triplet centroid is truly inside the ring
if ring_contains_point(coords, (xmean,ymean)):
return xmean,ymean
# failed to get sample point from this triplet
# remove oldest triplet coord to allow iterating to next triplet
triplet.pop(0)
else:
raise Exception('Unexpected error: Unable to find a ring sample point.')
def ring_contains_ring(coords1, coords2):
'''Returns True if all vertexes in coords2 are fully inside coords1.
'''
return all((ring_contains_point(coords1, p2) for p2 in coords2))
def organize_polygon_rings(rings):
'''Organize a list of coordinate rings into one or more polygons with holes.
Returns a list of polygons, where each polygon is composed of a single exterior
ring, and one or more interior holes.
Rings must be closed, and cannot intersect each other (non-self-intersecting polygon).
Rings are determined as exteriors if they run in clockwise direction, or interior
holes if they run in counter-clockwise direction. This method is used to construct
GeoJSON (multi)polygons from the shapefile polygon shape type, which does not
explicitly store the structure of the polygons beyond exterior/interior ring orientation.
'''
# first iterate rings and classify as exterior or hole
exteriors = []
holes = []
for ring in rings:
# shapefile format defines a polygon as a sequence of rings
# where exterior rings are clockwise, and holes counterclockwise
if signed_area(ring) < 0:
# ring is exterior
exteriors.append(ring)
else:
# ring is a hole
holes.append(ring)
# if only one exterior, then all holes belong to that exterior
if len(exteriors) == 1:
# exit early
poly = [exteriors[0]] + holes
polys = [poly]
return polys
# multiple exteriors, ie multi-polygon, have to group holes with correct exterior
# shapefile format does not specify which holes belong to which exteriors
# so have to do efficient multi-stage checking of hole-to-exterior containment
elif len(exteriors) > 1:
# exit early if no holes
if not holes:
polys = []
for ext in exteriors:
poly = [ext]
polys.append(poly)
return polys
# first determine each hole's candidate exteriors based on simple bbox contains test
hole_exteriors = dict([(hole_i,[]) for hole_i in xrange(len(holes))])
exterior_bboxes = [ring_bbox(ring) for ring in exteriors]
for hole_i in hole_exteriors.keys():
hole_bbox = ring_bbox(holes[hole_i])
for ext_i,ext_bbox in enumerate(exterior_bboxes):
if bbox_contains(ext_bbox, hole_bbox):
hole_exteriors[hole_i].append( ext_i )
# then, for holes with still more than one possible exterior, do more detailed hole-in-ring test
for hole_i,exterior_candidates in hole_exteriors.items():
if len(exterior_candidates) > 1:
# get hole sample point
hole_sample = ring_sample(holes[hole_i], ccw=True)
# collect new exterior candidates
new_exterior_candidates = []
for ext_i in exterior_candidates:
# check that hole sample point is inside exterior
hole_in_exterior = ring_contains_point(exteriors[ext_i], hole_sample)
if hole_in_exterior:
new_exterior_candidates.append(ext_i)
# set new exterior candidates
hole_exteriors[hole_i] = new_exterior_candidates
# if still holes with more than one possible exterior, means we have an exterior hole nested inside another exterior's hole
for hole_i,exterior_candidates in hole_exteriors.items():
if len(exterior_candidates) > 1:
# exterior candidate with the smallest area is the hole's most immediate parent
ext_i = sorted(exterior_candidates, key=lambda x: abs(signed_area(exteriors[x])))[0]
hole_exteriors[hole_i] = [ext_i]
# separate out holes that are orphaned (not contained by any exterior)
orphan_holes = []
for hole_i,exterior_candidates in list(hole_exteriors.items()):
if not exterior_candidates:
warnings.warn('Shapefile shape has invalid polygon: found orphan hole (not contained by any of the exteriors); interpreting as exterior.')
orphan_holes.append( hole_i )
del hole_exteriors[hole_i]
continue
# each hole should now only belong to one exterior, group into exterior-holes polygons
polys = []
for ext_i,ext in enumerate(exteriors):
poly = [ext]
# find relevant holes
poly_holes = []
for hole_i,exterior_candidates in list(hole_exteriors.items()):
# hole is relevant if previously matched with this exterior
if exterior_candidates[0] == ext_i:
poly_holes.append( holes[hole_i] )
poly += poly_holes
polys.append(poly)
# add orphan holes as exteriors
for hole_i in orphan_holes:
ext = holes[hole_i] # could potentially reverse their order, but in geojson winding order doesn't matter
poly = [ext]
polys.append(poly)
return polys
# no exteriors, be nice and assume due to incorrect winding order
else:
warnings.warn('Shapefile shape has invalid polygon: no exterior rings found (must have clockwise orientation); interpreting holes as exteriors.')
exteriors = holes # could potentially reverse their order, but in geojson winding order doesn't matter
polys = [[ext] for ext in exteriors]
return polys
class Shape(object):
def __init__(self, shapeType=NULL, points=None, parts=None, partTypes=None):
"""Stores the geometry of the different shape types
specified in the Shapefile spec. Shape types are
usually point, polyline, or polygons. Every shape type
except the "Null" type contains points at some level for
example vertices in a polygon. If a shape type has
multiple shapes containing points within a single
geometry record then those shapes are called parts. Parts
are designated by their starting index in geometry record's
list of shapes. For MultiPatch geometry, partTypes designates
the patch type of each of the parts.
"""
self.shapeType = shapeType
self.points = points or []
self.parts = parts or []
if partTypes:
self.partTypes = partTypes
@property
def __geo_interface__(self):
if self.shapeType in [POINT, POINTM, POINTZ]:
# point
if len(self.points) == 0:
# the shape has no coordinate information, i.e. is 'empty'
# the geojson spec does not define a proper null-geometry type
# however, it does allow geometry types with 'empty' coordinates to be interpreted as null-geometries
return {'type':'Point', 'coordinates':tuple()}
else:
return {
'type': 'Point',
'coordinates': tuple(self.points[0])
}
elif self.shapeType in [MULTIPOINT, MULTIPOINTM, MULTIPOINTZ]:
if len(self.points) == 0:
# the shape has no coordinate information, i.e. is 'empty'
# the geojson spec does not define a proper null-geometry type
# however, it does allow geometry types with 'empty' coordinates to be interpreted as null-geometries
return {'type':'MultiPoint', 'coordinates':[]}
else:
# multipoint
return {
'type': 'MultiPoint',
'coordinates': [tuple(p) for p in self.points]
}
elif self.shapeType in [POLYLINE, POLYLINEM, POLYLINEZ]:
if len(self.parts) == 0:
# the shape has no coordinate information, i.e. is 'empty'
# the geojson spec does not define a proper null-geometry type
# however, it does allow geometry types with 'empty' coordinates to be interpreted as null-geometries
return {'type':'LineString', 'coordinates':[]}
elif len(self.parts) == 1:
# linestring
return {
'type': 'LineString',
'coordinates': [tuple(p) for p in self.points]
}
else:
# multilinestring
ps = None
coordinates = []
for part in self.parts:
if ps == None:
ps = part
continue
else:
coordinates.append([tuple(p) for p in self.points[ps:part]])
ps = part
else:
coordinates.append([tuple(p) for p in self.points[part:]])
return {
'type': 'MultiLineString',
'coordinates': coordinates
}
elif self.shapeType in [POLYGON, POLYGONM, POLYGONZ]:
if len(self.parts) == 0:
# the shape has no coordinate information, i.e. is 'empty'
# the geojson spec does not define a proper null-geometry type
# however, it does allow geometry types with 'empty' coordinates to be interpreted as null-geometries
return {'type':'Polygon', 'coordinates':[]}
else:
# get all polygon rings
rings = []
for i in xrange(len(self.parts)):
# get indexes of start and end points of the ring
start = self.parts[i]
try:
end = self.parts[i+1]
except IndexError:
end = len(self.points)
# extract the points that make up the ring
ring = [tuple(p) for p in self.points[start:end]]
rings.append(ring)
# organize rings into list of polygons, where each polygon is defined as list of rings.
# the first ring is the exterior and any remaining rings are holes (same as GeoJSON).
polys = organize_polygon_rings(rings)
# return as geojson
if len(polys) == 1:
return {
'type': 'Polygon',
'coordinates': polys[0]
}
else:
return {
'type': 'MultiPolygon',
'coordinates': polys
}
else:
raise Exception('Shape type "%s" cannot be represented as GeoJSON.' % SHAPETYPE_LOOKUP[self.shapeType])
@staticmethod
def _from_geojson(geoj):
# create empty shape
shape = Shape()
# set shapeType
geojType = geoj["type"] if geoj else "Null"
if geojType == "Null":
shapeType = NULL
elif geojType == "Point":
shapeType = POINT
elif geojType == "LineString":
shapeType = POLYLINE
elif geojType == "Polygon":
shapeType = POLYGON
elif geojType == "MultiPoint":
shapeType = MULTIPOINT
elif geojType == "MultiLineString":
shapeType = POLYLINE
elif geojType == "MultiPolygon":
shapeType = POLYGON
else:
raise Exception("Cannot create Shape from GeoJSON type '%s'" % geojType)
shape.shapeType = shapeType
# set points and parts
if geojType == "Point":
shape.points = [ geoj["coordinates"] ]
shape.parts = [0]
elif geojType in ("MultiPoint","LineString"):
shape.points = geoj["coordinates"]
shape.parts = [0]
elif geojType in ("Polygon"):
points = []
parts = []
index = 0
for i,ext_or_hole in enumerate(geoj["coordinates"]):
if i == 0 and not signed_area(ext_or_hole) < 0:
# flip exterior direction
ext_or_hole = list(reversed(ext_or_hole))
elif i > 0 and not signed_area(ext_or_hole) >= 0:
# flip hole direction
ext_or_hole = list(reversed(ext_or_hole))
points.extend(ext_or_hole)
parts.append(index)
index += len(ext_or_hole)
shape.points = points
shape.parts = parts
elif geojType in ("MultiLineString"):
points = []
parts = []
index = 0
for linestring in geoj["coordinates"]:
points.extend(linestring)
parts.append(index)
index += len(linestring)
shape.points = points
shape.parts = parts
elif geojType in ("MultiPolygon"):
points = []
parts = []
index = 0
for polygon in geoj["coordinates"]:
for i,ext_or_hole in enumerate(polygon):
if i == 0 and not signed_area(ext_or_hole) < 0:
# flip exterior direction
ext_or_hole = list(reversed(ext_or_hole))
elif i > 0 and not signed_area(ext_or_hole) >= 0:
# flip hole direction
ext_or_hole = list(reversed(ext_or_hole))
points.extend(ext_or_hole)
parts.append(index)
index += len(ext_or_hole)
shape.points = points
shape.parts = parts
return shape
@property
def shapeTypeName(self):
return SHAPETYPE_LOOKUP[self.shapeType]
class _Record(list):
"""
A class to hold a record. Subclasses list to ensure compatibility with
former work and to reuse all the optimizations of the builtin list.
In addition to the list interface, the values of the record
can also be retrieved using the field's name. For example if the dbf contains
a field ID at position 0, the ID can be retrieved with the position, the field name
as a key, or the field name as an attribute.
>>> # Create a Record with one field, normally the record is created by the Reader class
>>> r = _Record({'ID': 0}, [0])
>>> print(r[0])
>>> print(r['ID'])
>>> print(r.ID)
"""
def __init__(self, field_positions, values, oid=None):
"""
A Record should be created by the Reader class
:param field_positions: A dict mapping field names to field positions
:param values: A sequence of values
:param oid: The object id, an int (optional)
"""
self.__field_positions = field_positions
if oid is not None:
self.__oid = oid
else:
self.__oid = -1
list.__init__(self, values)
def __getattr__(self, item):
"""
__getattr__ is called if an attribute is used that does
not exist in the normal sense. For example r=Record(...), r.ID
calls r.__getattr__('ID'), but r.index(5) calls list.index(r, 5)
:param item: The field name, used as attribute
:return: Value of the field
:raises: AttributeError, if item is not a field of the shapefile
and IndexError, if the field exists but the field's
corresponding value in the Record does not exist
"""
try:
index = self.__field_positions[item]
return list.__getitem__(self, index)
except KeyError:
raise AttributeError('{} is not a field name'.format(item))
except IndexError:
raise IndexError('{} found as a field but not enough values available.'.format(item))
def __setattr__(self, key, value):
"""
Sets a value of a field attribute
:param key: The field name
:param value: the value of that field
:return: None
:raises: AttributeError, if key is not a field of the shapefile
"""
if key.startswith('_'): # Prevent infinite loop when setting mangled attribute
return list.__setattr__(self, key, value)
try:
index = self.__field_positions[key]
return list.__setitem__(self, index, value)
except KeyError:
raise AttributeError('{} is not a field name'.format(key))
def __getitem__(self, item):
"""
Extends the normal list item access with
access using a fieldname
For example r['ID'], r[0]
:param item: Either the position of the value or the name of a field
:return: the value of the field
"""
try:
return list.__getitem__(self, item)
except TypeError:
try:
index = self.__field_positions[item]
except KeyError:
index = None
if index is not None:
return list.__getitem__(self, index)
else:
raise IndexError('"{}" is not a field name and not an int'.format(item))
def __setitem__(self, key, value):
"""
Extends the normal list item access with
access using a fieldname
For example r['ID']=2, r[0]=2
:param key: Either the position of the value or the name of a field
:param value: the new value of the field
"""
try:
return list.__setitem__(self, key, value)
except TypeError:
index = self.__field_positions.get(key)
if index is not None:
return list.__setitem__(self, index, value)
else:
raise IndexError('{} is not a field name and not an int'.format(key))
@property
def oid(self):
"""The index position of the record in the original shapefile"""
return self.__oid
def as_dict(self, date_strings=False):
"""
Returns this Record as a dictionary using the field names as keys
:return: dict
"""
dct = dict((f, self[i]) for f, i in self.__field_positions.items())
if date_strings:
for k,v in dct.items():
if isinstance(v, date):
dct[k] = '{:04d}{:02d}{:02d}'.format(v.year, v.month, v.day)
return dct
def __repr__(self):
return 'Record #{}: {}'.format(self.__oid, list(self))
def __dir__(self):
"""
Helps to show the field names in an interactive environment like IPython.
See: http://ipython.readthedocs.io/en/stable/config/integrating.html
:return: List of method names and fields
"""
default = list(dir(type(self))) # default list methods and attributes of this class
fnames = list(self.__field_positions.keys()) # plus field names (random order if Python version < 3.6)
return default + fnames
class ShapeRecord(object):
"""A ShapeRecord object containing a shape along with its attributes.
Provides the GeoJSON __geo_interface__ to return a Feature dictionary."""
def __init__(self, shape=None, record=None):
self.shape = shape
self.record = record
@property
def __geo_interface__(self):
return {'type': 'Feature',
'properties': self.record.as_dict(date_strings=True),
'geometry': None if self.shape.shapeType == NULL else self.shape.__geo_interface__}
class Shapes(list):
"""A class to hold a list of Shape objects. Subclasses list to ensure compatibility with
former work and to reuse all the optimizations of the builtin list.
In addition to the list interface, this also provides the GeoJSON __geo_interface__
to return a GeometryCollection dictionary."""
def __repr__(self):
return 'Shapes: {}'.format(list(self))
@property
def __geo_interface__(self):
# Note: currently this will fail if any of the shapes are null-geometries
# could be fixed by storing the shapefile shapeType upon init, returning geojson type with empty coords
return {'type': 'GeometryCollection',
'geometries': [shape.__geo_interface__ for shape in self]}
class ShapeRecords(list):
"""A class to hold a list of ShapeRecord objects. Subclasses list to ensure compatibility with
former work and to reuse all the optimizations of the builtin list.
In addition to the list interface, this also provides the GeoJSON __geo_interface__
to return a FeatureCollection dictionary."""
def __repr__(self):
return 'ShapeRecords: {}'.format(list(self))
@property
def __geo_interface__(self):
return {'type': 'FeatureCollection',
'features': [shaperec.__geo_interface__ for shaperec in self]}
class ShapefileException(Exception):
"""An exception to handle shapefile specific problems."""
pass
class Reader(object):
"""Reads the three files of a shapefile as a unit or
separately. If one of the three files (.shp, .shx,
.dbf) is missing no exception is thrown until you try
to call a method that depends on that particular file.
The .shx index file is used if available for efficiency
but is not required to read the geometry from the .shp
file. The "shapefile" argument in the constructor is the
name of the file you want to open.
You can instantiate a Reader without specifying a shapefile
and then specify one later with the load() method.
Only the shapefile headers are read upon loading. Content
within each file is only accessed when required and as
efficiently as possible. Shapefiles are usually not large
but they can be.
"""
def __init__(self, *args, **kwargs):
self.shp = None
self.shx = None
self.dbf = None
self.shapeName = "Not specified"
self._offsets = []
self.shpLength = None
self.numRecords = None
self.numShapes = None
self.fields = []
self.__dbfHdrLength = 0
self.__fieldposition_lookup = {}
self.encoding = kwargs.pop('encoding', 'utf-8')
self.encodingErrors = kwargs.pop('encodingErrors', 'strict')
# See if a shapefile name was passed as the first argument
if len(args) > 0:
if is_string(args[0]):
self.load(args[0])
return
# Otherwise, load from separate shp/shx/dbf args (must be file-like)
if "shp" in kwargs.keys():
if hasattr(kwargs["shp"], "read"):
self.shp = kwargs["shp"]
# Copy if required
try:
self.shp.seek(0)
except (NameError, io.UnsupportedOperation):
self.shp = io.BytesIO(self.shp.read())
else:
raise ShapefileException('The shp arg must be file-like.')
if "shx" in kwargs.keys():
if hasattr(kwargs["shx"], "read"):
self.shx = kwargs["shx"]
# Copy if required
try:
self.shx.seek(0)
except (NameError, io.UnsupportedOperation):
self.shx = io.BytesIO(self.shx.read())
else:
raise ShapefileException('The shx arg must be file-like.')
if "dbf" in kwargs.keys():
if hasattr(kwargs["dbf"], "read"):
self.dbf = kwargs["dbf"]
# Copy if required
try:
self.dbf.seek(0)
except (NameError, io.UnsupportedOperation):
self.dbf = io.BytesIO(self.dbf.read())
else:
raise ShapefileException('The dbf arg must be file-like.')
# Load the files
if self.shp or self.dbf:
self.load()
def __str__(self):
"""
Use some general info on the shapefile as __str__
"""
info = ['shapefile Reader']
if self.shp:
info.append(" {} shapes (type '{}')".format(
len(self), SHAPETYPE_LOOKUP[self.shapeType]))
if self.dbf:
info.append(' {} records ({} fields)'.format(
len(self), len(self.fields)))
return '\n'.join(info)
def __enter__(self):
"""
Enter phase of context manager.
"""
return self
def __exit__(self, exc_type, exc_val, exc_tb):
"""
Exit phase of context manager, close opened files.
"""
self.close()
def __len__(self):
"""Returns the number of shapes/records in the shapefile."""
if self.dbf:
# Preferably use dbf record count
if self.numRecords is None:
self.__dbfHeader()
return self.numRecords
elif self.shp:
# Otherwise use shape count
if self.shx:
# Use index file to get total count
if self.numShapes is None:
# File length (16-bit word * 2 = bytes) - header length
self.shx.seek(24)
shxRecordLength = (unpack(">i", self.shx.read(4))[0] * 2) - 100
self.numShapes = shxRecordLength // 8
return self.numShapes
else:
# Index file not available, iterate all shapes to get total count
if self.numShapes is None:
i = 0
for i,shape in enumerate(self.iterShapes()):
i += 1
self.numShapes = i
return self.numShapes
else:
# No file loaded yet, treat as 'empty' shapefile
return 0
def __iter__(self):
"""Iterates through the shapes/records in the shapefile."""
for shaperec in self.iterShapeRecords():
yield shaperec
@property
def __geo_interface__(self):
shaperecords = self.shapeRecords()
fcollection = shaperecords.__geo_interface__
fcollection['bbox'] = list(self.bbox)
return fcollection
@property
def shapeTypeName(self):
return SHAPETYPE_LOOKUP[self.shapeType]
def load(self, shapefile=None):
"""Opens a shapefile from a filename or file-like
object. Normally this method would be called by the
constructor with the file name as an argument."""
if shapefile:
(shapeName, ext) = os.path.splitext(shapefile)
self.shapeName = shapeName
self.load_shp(shapeName)
self.load_shx(shapeName)
self.load_dbf(shapeName)
if not (self.shp or self.dbf):
raise ShapefileException("Unable to open %s.dbf or %s.shp." % (shapeName, shapeName))
if self.shp:
self.__shpHeader()
if self.dbf:
self.__dbfHeader()
def load_shp(self, shapefile_name):
"""
Attempts to load file with .shp extension as both lower and upper case
"""
shp_ext = 'shp'
try:
self.shp = open("%s.%s" % (shapefile_name, shp_ext), "rb")
except IOError:
try:
self.shp = open("%s.%s" % (shapefile_name, shp_ext.upper()), "rb")
except IOError:
pass
def load_shx(self, shapefile_name):
"""
Attempts to load file with .shx extension as both lower and upper case
"""
shx_ext = 'shx'
try:
self.shx = open("%s.%s" % (shapefile_name, shx_ext), "rb")
except IOError:
try:
self.shx = open("%s.%s" % (shapefile_name, shx_ext.upper()), "rb")
except IOError:
pass
def load_dbf(self, shapefile_name):
"""
Attempts to load file with .dbf extension as both lower and upper case
"""
dbf_ext = 'dbf'
try:
self.dbf = open("%s.%s" % (shapefile_name, dbf_ext), "rb")
except IOError:
try:
self.dbf = open("%s.%s" % (shapefile_name, dbf_ext.upper()), "rb")
except IOError:
pass
def __del__(self):
self.close()
def close(self):
for attribute in (self.shp, self.shx, self.dbf):
if hasattr(attribute, 'close'):
try:
attribute.close()
except IOError:
pass
def __getFileObj(self, f):
"""Checks to see if the requested shapefile file object is
available. If not a ShapefileException is raised."""
if not f:
raise ShapefileException("Shapefile Reader requires a shapefile or file-like object.")
if self.shp and self.shpLength is None:
self.load()
if self.dbf and len(self.fields) == 0:
self.load()
return f