/usr/lib/python2.7/dist-packages/shapefile.py is in python-pyshp 1.2.3+ds-1.
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shapefile.py
Provides read and write support for ESRI Shapefiles.
author: jlawhead<at>geospatialpython.com
date: 2015/06/22
version: 1.2.3
Compatible with Python versions 2.4-3.x
version changelog: Reader.iterShapeRecords() bugfix for Python 3
"""
__version__ = "1.2.3"
from struct import pack, unpack, calcsize, error
import os
import sys
import time
import array
import tempfile
import itertools
#
# 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
PYTHON3 = sys.version_info[0] == 3
if PYTHON3:
xrange = range
izip = zip
else:
from itertools import izip
def b(v):
if PYTHON3:
if isinstance(v, str):
# For python 3 encode str to bytes.
return v.encode('utf-8')
elif isinstance(v, bytes):
# Already bytes.
return v
else:
# Error.
raise Exception('Unknown input type')
else:
# For python 2 assume str passed in and return str.
return v
def u(v):
if PYTHON3:
# try/catch added 2014/05/07
# returned error on dbf of shapefile
# from www.naturalearthdata.com named
# "ne_110m_admin_0_countries".
# Just returning v as is seemed to fix
# the problem. This function could
# be condensed further.
try:
if isinstance(v, bytes):
# For python 3 decode bytes to str.
return v.decode('utf-8')
elif isinstance(v, str):
# Already str.
return v
else:
# Error.
raise Exception('Unknown input type')
except: return v
else:
# For python 2 assume str passed in and return str.
return v
def is_string(v):
if PYTHON3:
return isinstance(v, str)
else:
return isinstance(v, basestring)
class _Array(array.array):
"""Converts python tuples to lits 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 at http://www.cgafaq.info/wiki/Polygon_Area. A value >= 0
indicates a counter-clockwise oriented ring.
"""
xs, ys = map(list, zip(*coords))
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
class _Shape:
def __init__(self, shapeType=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 verticies 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."""
self.shapeType = shapeType
self.points = []
@property
def __geo_interface__(self):
if self.shapeType in [POINT, POINTM, POINTZ]:
return {
'type': 'Point',
'coordinates': tuple(self.points[0])
}
elif self.shapeType in [MULTIPOINT, MULTIPOINTM, MULTIPOINTZ]:
return {
'type': 'MultiPoint',
'coordinates': tuple([tuple(p) for p in self.points])
}
elif self.shapeType in [POLYLINE, POLYLINEM, POLYLINEZ]:
if len(self.parts) == 1:
return {
'type': 'LineString',
'coordinates': tuple([tuple(p) for p in self.points])
}
else:
ps = None
coordinates = []
for part in self.parts:
if ps == None:
ps = part
continue
else:
coordinates.append(tuple([tuple(p) for p in self.points[ps:part]]))
ps = part
else:
coordinates.append(tuple([tuple(p) for p in self.points[part:]]))
return {
'type': 'MultiLineString',
'coordinates': tuple(coordinates)
}
elif self.shapeType in [POLYGON, POLYGONM, POLYGONZ]:
if len(self.parts) == 1:
return {
'type': 'Polygon',
'coordinates': (tuple([tuple(p) for p in self.points]),)
}
else:
ps = None
coordinates = []
for part in self.parts:
if ps == None:
ps = part
continue
else:
coordinates.append(tuple([tuple(p) for p in self.points[ps:part]]))
ps = part
else:
coordinates.append(tuple([tuple(p) for p in self.points[part:]]))
polys = []
poly = [coordinates[0]]
for coord in coordinates[1:]:
if signed_area(coord) < 0:
polys.append(poly)
poly = [coord]
else:
poly.append(coord)
polys.append(poly)
if len(polys) == 1:
return {
'type': 'Polygon',
'coordinates': tuple(polys[0])
}
elif len(polys) > 1:
return {
'type': 'MultiPolygon',
'coordinates': polys
}
class _ShapeRecord:
"""A shape object of any type."""
def __init__(self, shape=None, record=None):
self.shape = shape
self.record = record
class ShapefileException(Exception):
"""An exception to handle shapefile specific problems."""
pass
class Reader:
"""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.fields = []
self.__dbfHdrLength = 0
# See if a shapefile name was passed as an argument
if len(args) > 0:
if is_string(args[0]):
self.load(args[0])
return
if "shp" in kwargs.keys():
if hasattr(kwargs["shp"], "read"):
self.shp = kwargs["shp"]
if hasattr(self.shp, "seek"):
self.shp.seek(0)
if "shx" in kwargs.keys():
if hasattr(kwargs["shx"], "read"):
self.shx = kwargs["shx"]
if hasattr(self.shx, "seek"):
self.shx.seek(0)
if "dbf" in kwargs.keys():
if hasattr(kwargs["dbf"], "read"):
self.dbf = kwargs["dbf"]
if hasattr(self.dbf, "seek"):
self.dbf.seek(0)
if self.shp or self.dbf:
self.load()
else:
raise ShapefileException("Shapefile Reader requires a shapefile or file-like object.")
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 object or file name as an
argument."""
if shapefile:
(shapeName, ext) = os.path.splitext(shapefile)
self.shapeName = shapeName
try:
self.shp = open("%s.shp" % shapeName, "rb")
except IOError:
raise ShapefileException("Unable to open %s.shp" % shapeName)
try:
self.shx = open("%s.shx" % shapeName, "rb")
except IOError:
raise ShapefileException("Unable to open %s.shx" % shapeName)
try:
self.dbf = open("%s.dbf" % shapeName, "rb")
except IOError:
raise ShapefileException("Unable to open %s.dbf" % shapeName)
if self.shp:
self.__shpHeader()
if self.dbf:
self.__dbfHeader()
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
def __restrictIndex(self, i):
"""Provides list-like handling of a record index with a clearer
error message if the index is out of bounds."""
if self.numRecords:
rmax = self.numRecords - 1
if abs(i) > rmax:
raise IndexError("Shape or Record index out of range.")
if i < 0: i = range(self.numRecords)[i]
return i
def __shpHeader(self):
"""Reads the header information from a .shp or .shx file."""
if not self.shp:
raise ShapefileException("Shapefile Reader requires a shapefile or file-like object. (no shp file found")
shp = self.shp
# File length (16-bit word * 2 = bytes)
shp.seek(24)
self.shpLength = unpack(">i", shp.read(4))[0] * 2
# Shape type
shp.seek(32)
self.shapeType= unpack("<i", shp.read(4))[0]
# The shapefile's bounding box (lower left, upper right)
self.bbox = _Array('d', unpack("<4d", shp.read(32)))
# Elevation
self.elevation = _Array('d', unpack("<2d", shp.read(16)))
# Measure
self.measure = _Array('d', unpack("<2d", shp.read(16)))
def __shape(self):
"""Returns the header info and geometry for a single shape."""
f = self.__getFileObj(self.shp)
record = _Shape()
nParts = nPoints = zmin = zmax = mmin = mmax = None
(recNum, recLength) = unpack(">2i", f.read(8))
# Determine the start of the next record
next = f.tell() + (2 * recLength)
shapeType = unpack("<i", f.read(4))[0]
record.shapeType = shapeType
# For Null shapes create an empty points list for consistency
if shapeType == 0:
record.points = []
# All shape types capable of having a bounding box
elif shapeType in (3,5,8,13,15,18,23,25,28,31):
record.bbox = _Array('d', unpack("<4d", f.read(32)))
# Shape types with parts
if shapeType in (3,5,13,15,23,25,31):
nParts = unpack("<i", f.read(4))[0]
# Shape types with points
if shapeType in (3,5,8,13,15,23,25,31):
nPoints = unpack("<i", f.read(4))[0]
# Read parts
if nParts:
record.parts = _Array('i', unpack("<%si" % nParts, f.read(nParts * 4)))
# Read part types for Multipatch - 31
if shapeType == 31:
record.partTypes = _Array('i', unpack("<%si" % nParts, f.read(nParts * 4)))
# Read points - produces a list of [x,y] values
if nPoints:
record.points = [_Array('d', unpack("<2d", f.read(16))) for p in range(nPoints)]
# Read z extremes and values
if shapeType in (13,15,18,31):
(zmin, zmax) = unpack("<2d", f.read(16))
record.z = _Array('d', unpack("<%sd" % nPoints, f.read(nPoints * 8)))
# Read m extremes and values if header m values do not equal 0.0
if shapeType in (13,15,18,23,25,28,31) and not 0.0 in self.measure:
(mmin, mmax) = unpack("<2d", f.read(16))
# Measure values less than -10e38 are nodata values according to the spec
record.m = []
for m in _Array('d', unpack("<%sd" % nPoints, f.read(nPoints * 8))):
if m > -10e38:
record.m.append(m)
else:
record.m.append(None)
# Read a single point
if shapeType in (1,11,21):
record.points = [_Array('d', unpack("<2d", f.read(16)))]
# Read a single Z value
if shapeType == 11:
record.z = unpack("<d", f.read(8))
# Read a single M value
if shapeType in (11,21):
record.m = unpack("<d", f.read(8))
# Seek to the end of this record as defined by the record header because
# the shapefile spec doesn't require the actual content to meet the header
# definition. Probably allowed for lazy feature deletion.
f.seek(next)
return record
def __shapeIndex(self, i=None):
"""Returns the offset in a .shp file for a shape based on information
in the .shx index file."""
shx = self.shx
if not shx:
return None
if not self._offsets:
# File length (16-bit word * 2 = bytes) - header length
shx.seek(24)
shxRecordLength = (unpack(">i", shx.read(4))[0] * 2) - 100
numRecords = shxRecordLength // 8
# Jump to the first record.
shx.seek(100)
for r in range(numRecords):
# Offsets are 16-bit words just like the file length
self._offsets.append(unpack(">i", shx.read(4))[0] * 2)
shx.seek(shx.tell() + 4)
if not i == None:
return self._offsets[i]
def shape(self, i=0):
"""Returns a shape object for a shape in the the geometry
record file."""
shp = self.__getFileObj(self.shp)
i = self.__restrictIndex(i)
offset = self.__shapeIndex(i)
if not offset:
# Shx index not available so iterate the full list.
for j,k in enumerate(self.iterShapes()):
if j == i:
return k
shp.seek(offset)
return self.__shape()
def shapes(self):
"""Returns all shapes in a shapefile."""
shp = self.__getFileObj(self.shp)
# Found shapefiles which report incorrect
# shp file length in the header. Can't trust
# that so we seek to the end of the file
# and figure it out.
shp.seek(0,2)
self.shpLength = shp.tell()
shp.seek(100)
shapes = []
while shp.tell() < self.shpLength:
shapes.append(self.__shape())
return shapes
def iterShapes(self):
"""Serves up shapes in a shapefile as an iterator. Useful
for handling large shapefiles."""
shp = self.__getFileObj(self.shp)
shp.seek(0,2)
self.shpLength = shp.tell()
shp.seek(100)
while shp.tell() < self.shpLength:
yield self.__shape()
def __dbfHeaderLength(self):
"""Retrieves the header length of a dbf file header."""
if not self.__dbfHdrLength:
if not self.dbf:
raise ShapefileException("Shapefile Reader requires a shapefile or file-like object. (no dbf file found)")
dbf = self.dbf
(self.numRecords, self.__dbfHdrLength) = \
unpack("<xxxxLH22x", dbf.read(32))
return self.__dbfHdrLength
def __dbfHeader(self):
"""Reads a dbf header. Xbase-related code borrows heavily from ActiveState Python Cookbook Recipe 362715 by Raymond Hettinger"""
if not self.dbf:
raise ShapefileException("Shapefile Reader requires a shapefile or file-like object. (no dbf file found)")
dbf = self.dbf
headerLength = self.__dbfHeaderLength()
numFields = (headerLength - 33) // 32
for field in range(numFields):
fieldDesc = list(unpack("<11sc4xBB14x", dbf.read(32)))
name = 0
idx = 0
if b("\x00") in fieldDesc[name]:
idx = fieldDesc[name].index(b("\x00"))
else:
idx = len(fieldDesc[name]) - 1
fieldDesc[name] = fieldDesc[name][:idx]
fieldDesc[name] = u(fieldDesc[name])
fieldDesc[name] = fieldDesc[name].lstrip()
fieldDesc[1] = u(fieldDesc[1])
self.fields.append(fieldDesc)
terminator = dbf.read(1)
if terminator != b("\r"):
raise ShapefileException("Shapefile dbf header lacks expected terminator. (likely corrupt?)")
self.fields.insert(0, ('DeletionFlag', 'C', 1, 0))
def __recordFmt(self):
"""Calculates the size of a .shp geometry record."""
if not self.numRecords:
self.__dbfHeader()
fmt = ''.join(['%ds' % fieldinfo[2] for fieldinfo in self.fields])
fmtSize = calcsize(fmt)
return (fmt, fmtSize)
def __record(self):
"""Reads and returns a dbf record row as a list of values."""
f = self.__getFileObj(self.dbf)
recFmt = self.__recordFmt()
recordContents = unpack(recFmt[0], f.read(recFmt[1]))
if recordContents[0] != b(' '):
# deleted record
return None
record = []
for (name, typ, size, deci), value in zip(self.fields,
recordContents):
if name == 'DeletionFlag':
continue
elif not value.strip():
record.append(value)
continue
elif typ == "N":
value = value.replace(b('\0'), b('')).strip()
value = value.replace(b('*'), b('')) # QGIS NULL is all '*' chars
if value == b(''):
value = None
elif deci:
value = float(value)
else:
value = int(value)
elif typ == b('D'):
if value.count(b('0')) == len(value): # QGIS NULL is all '0' chars
value = None
else:
try:
y, m, d = int(value[:4]), int(value[4:6]), int(value[6:8])
value = [y, m, d]
except:
value = value.strip()
elif typ == b('L'):
value = (value in b('YyTt') and b('T')) or \
(value in b('NnFf') and b('F')) or b('?')
else:
value = u(value)
value = value.strip()
record.append(value)
return record
def record(self, i=0):
"""Returns a specific dbf record based on the supplied index."""
f = self.__getFileObj(self.dbf)
if not self.numRecords:
self.__dbfHeader()
i = self.__restrictIndex(i)
recSize = self.__recordFmt()[1]
f.seek(0)
f.seek(self.__dbfHeaderLength() + (i * recSize))
return self.__record()
def records(self):
"""Returns all records in a dbf file."""
if not self.numRecords:
self.__dbfHeader()
records = []
f = self.__getFileObj(self.dbf)
f.seek(self.__dbfHeaderLength())
for i in range(self.numRecords):
r = self.__record()
if r:
records.append(r)
return records
def iterRecords(self):
"""Serves up records in a dbf file as an iterator.
Useful for large shapefiles or dbf files."""
if not self.numRecords:
self.__dbfHeader()
f = self.__getFileObj(self.dbf)
f.seek(self.__dbfHeaderLength())
for i in xrange(self.numRecords):
r = self.__record()
if r:
yield r
def shapeRecord(self, i=0):
"""Returns a combination geometry and attribute record for the
supplied record index."""
i = self.__restrictIndex(i)
return _ShapeRecord(shape=self.shape(i), record=self.record(i))
def shapeRecords(self):
"""Returns a list of combination geometry/attribute records for
all records in a shapefile."""
shapeRecords = []
return [_ShapeRecord(shape=rec[0], record=rec[1]) \
for rec in zip(self.shapes(), self.records())]
def iterShapeRecords(self):
"""Returns a generator of combination geometry/attribute records for
all records in a shapefile."""
for shape, record in izip(self.iterShapes(), self.iterRecords()):
yield _ShapeRecord(shape=shape, record=record)
class Writer:
"""Provides write support for ESRI Shapefiles."""
def __init__(self, shapeType=None):
self._shapes = []
self.fields = []
self.records = []
self.shapeType = shapeType
self.shp = None
self.shx = None
self.dbf = None
# Geometry record offsets and lengths for writing shx file.
self._offsets = []
self._lengths = []
# Use deletion flags in dbf? Default is false (0).
self.deletionFlag = 0
def __getFileObj(self, f):
"""Safety handler to verify file-like objects"""
if not f:
raise ShapefileException("No file-like object available.")
elif hasattr(f, "write"):
return f
else:
pth = os.path.split(f)[0]
if pth and not os.path.exists(pth):
os.makedirs(pth)
return open(f, "wb")
def __shpFileLength(self):
"""Calculates the file length of the shp file."""
# Start with header length
size = 100
# Calculate size of all shapes
for s in self._shapes:
# Add in record header and shape type fields
size += 12
# nParts and nPoints do not apply to all shapes
#if self.shapeType not in (0,1):
# nParts = len(s.parts)
# nPoints = len(s.points)
if hasattr(s,'parts'):
nParts = len(s.parts)
if hasattr(s,'points'):
nPoints = len(s.points)
# All shape types capable of having a bounding box
if self.shapeType in (3,5,8,13,15,18,23,25,28,31):
size += 32
# Shape types with parts
if self.shapeType in (3,5,13,15,23,25,31):
# Parts count
size += 4
# Parts index array
size += nParts * 4
# Shape types with points
if self.shapeType in (3,5,8,13,15,23,25,31):
# Points count
size += 4
# Points array
size += 16 * nPoints
# Calc size of part types for Multipatch (31)
if self.shapeType == 31:
size += nParts * 4
# Calc z extremes and values
if self.shapeType in (13,15,18,31):
# z extremes
size += 16
# z array
size += 8 * nPoints
# Calc m extremes and values
if self.shapeType in (23,25,31):
# m extremes
size += 16
# m array
size += 8 * nPoints
# Calc a single point
if self.shapeType in (1,11,21):
size += 16
# Calc a single Z value
if self.shapeType == 11:
size += 8
# Calc a single M value
if self.shapeType in (11,21):
size += 8
# Calculate size as 16-bit words
size //= 2
return size
def __bbox(self, shapes, shapeTypes=[]):
x = []
y = []
for s in shapes:
shapeType = self.shapeType
if shapeTypes:
shapeType = shapeTypes[shapes.index(s)]
px, py = list(zip(*s.points))[:2]
x.extend(px)
y.extend(py)
return [min(x), min(y), max(x), max(y)]
def __zbox(self, shapes, shapeTypes=[]):
z = []
for s in shapes:
try:
for p in s.points:
z.append(p[2])
except IndexError:
pass
if not z: z.append(0)
return [min(z), max(z)]
def __mbox(self, shapes, shapeTypes=[]):
m = [0]
for s in shapes:
try:
for p in s.points:
m.append(p[3])
except IndexError:
pass
return [min(m), max(m)]
def bbox(self):
"""Returns the current bounding box for the shapefile which is
the lower-left and upper-right corners. It does not contain the
elevation or measure extremes."""
return self.__bbox(self._shapes)
def zbox(self):
"""Returns the current z extremes for the shapefile."""
return self.__zbox(self._shapes)
def mbox(self):
"""Returns the current m extremes for the shapefile."""
return self.__mbox(self._shapes)
def __shapefileHeader(self, fileObj, headerType='shp'):
"""Writes the specified header type to the specified file-like object.
Several of the shapefile formats are so similar that a single generic
method to read or write them is warranted."""
f = self.__getFileObj(fileObj)
f.seek(0)
# File code, Unused bytes
f.write(pack(">6i", 9994,0,0,0,0,0))
# File length (Bytes / 2 = 16-bit words)
if headerType == 'shp':
f.write(pack(">i", self.__shpFileLength()))
elif headerType == 'shx':
f.write(pack('>i', ((100 + (len(self._shapes) * 8)) // 2)))
# Version, Shape type
f.write(pack("<2i", 1000, self.shapeType))
# The shapefile's bounding box (lower left, upper right)
if self.shapeType != 0:
try:
f.write(pack("<4d", *self.bbox()))
except error:
raise ShapefileException("Failed to write shapefile bounding box. Floats required.")
else:
f.write(pack("<4d", 0,0,0,0))
# Elevation
z = self.zbox()
# Measure
m = self.mbox()
try:
f.write(pack("<4d", z[0], z[1], m[0], m[1]))
except error:
raise ShapefileException("Failed to write shapefile elevation and measure values. Floats required.")
def __dbfHeader(self):
"""Writes the dbf header and field descriptors."""
f = self.__getFileObj(self.dbf)
f.seek(0)
version = 3
year, month, day = time.localtime()[:3]
year -= 1900
# Remove deletion flag placeholder from fields
for field in self.fields:
if field[0].startswith("Deletion"):
self.fields.remove(field)
numRecs = len(self.records)
numFields = len(self.fields)
headerLength = numFields * 32 + 33
recordLength = sum([int(field[2]) for field in self.fields]) + 1
header = pack('<BBBBLHH20x', version, year, month, day, numRecs,
headerLength, recordLength)
f.write(header)
# Field descriptors
for field in self.fields:
name, fieldType, size, decimal = field
name = b(name)
name = name.replace(b(' '), b('_'))
name = name.ljust(11).replace(b(' '), b('\x00'))
fieldType = b(fieldType)
size = int(size)
fld = pack('<11sc4xBB14x', name, fieldType, size, decimal)
f.write(fld)
# Terminator
f.write(b('\r'))
def __shpRecords(self):
"""Write the shp records"""
f = self.__getFileObj(self.shp)
f.seek(100)
recNum = 1
for s in self._shapes:
self._offsets.append(f.tell())
# Record number, Content length place holder
f.write(pack(">2i", recNum, 0))
recNum += 1
start = f.tell()
# Shape Type
if self.shapeType != 31:
s.shapeType = self.shapeType
f.write(pack("<i", s.shapeType))
# All shape types capable of having a bounding box
if s.shapeType in (3,5,8,13,15,18,23,25,28,31):
try:
f.write(pack("<4d", *self.__bbox([s])))
except error:
raise ShapefileException("Falied to write bounding box for record %s. Expected floats." % recNum)
# Shape types with parts
if s.shapeType in (3,5,13,15,23,25,31):
# Number of parts
f.write(pack("<i", len(s.parts)))
# Shape types with multiple points per record
if s.shapeType in (3,5,8,13,15,23,25,31):
# Number of points
f.write(pack("<i", len(s.points)))
# Write part indexes
if s.shapeType in (3,5,13,15,23,25,31):
for p in s.parts:
f.write(pack("<i", p))
# Part types for Multipatch (31)
if s.shapeType == 31:
for pt in s.partTypes:
f.write(pack("<i", pt))
# Write points for multiple-point records
if s.shapeType in (3,5,8,13,15,23,25,31):
try:
[f.write(pack("<2d", *p[:2])) for p in s.points]
except error:
raise ShapefileException("Failed to write points for record %s. Expected floats." % recNum)
# Write z extremes and values
if s.shapeType in (13,15,18,31):
try:
f.write(pack("<2d", *self.__zbox([s])))
except error:
raise ShapefileException("Failed to write elevation extremes for record %s. Expected floats." % recNum)
try:
if hasattr(s,"z"):
f.write(pack("<%sd" % len(s.z), *s.z))
else:
[f.write(pack("<d", p[2])) for p in s.points]
except error:
raise ShapefileException("Failed to write elevation values for record %s. Expected floats." % recNum)
# Write m extremes and values
if s.shapeType in (13,15,18,23,25,28,31):
try:
if hasattr(s,"m"):
f.write(pack("<%sd" % len(s.m), *s.m))
else:
f.write(pack("<2d", *self.__mbox([s])))
except error:
raise ShapefileException("Failed to write measure extremes for record %s. Expected floats" % recNum)
try:
[f.write(pack("<d", p[3])) for p in s.points]
except error:
raise ShapefileException("Failed to write measure values for record %s. Expected floats" % recNum)
# Write a single point
if s.shapeType in (1,11,21):
try:
f.write(pack("<2d", s.points[0][0], s.points[0][1]))
except error:
raise ShapefileException("Failed to write point for record %s. Expected floats." % recNum)
# Write a single Z value
if s.shapeType == 11:
if hasattr(s, "z"):
try:
if not s.z:
s.z = (0,)
f.write(pack("<d", s.z[0]))
except error:
raise ShapefileException("Failed to write elevation value for record %s. Expected floats." % recNum)
else:
try:
if len(s.points[0])<3:
s.points[0].append(0)
f.write(pack("<d", s.points[0][2]))
except error:
raise ShapefileException("Failed to write elevation value for record %s. Expected floats." % recNum)
# Write a single M value
if s.shapeType in (11,21):
if hasattr(s, "m"):
try:
if not s.m:
s.m = (0,)
f.write(pack("<1d", s.m[0]))
except error:
raise ShapefileException("Failed to write measure value for record %s. Expected floats." % recNum)
else:
try:
if len(s.points[0])<4:
s.points[0].append(0)
f.write(pack("<1d", s.points[0][3]))
except error:
raise ShapefileException("Failed to write measure value for record %s. Expected floats." % recNum)
# Finalize record length as 16-bit words
finish = f.tell()
length = (finish - start) // 2
self._lengths.append(length)
# start - 4 bytes is the content length field
f.seek(start-4)
f.write(pack(">i", length))
f.seek(finish)
def __shxRecords(self):
"""Writes the shx records."""
f = self.__getFileObj(self.shx)
f.seek(100)
for i in range(len(self._shapes)):
f.write(pack(">i", self._offsets[i] // 2))
f.write(pack(">i", self._lengths[i]))
def __dbfRecords(self):
"""Writes the dbf records."""
f = self.__getFileObj(self.dbf)
for record in self.records:
if not self.fields[0][0].startswith("Deletion"):
f.write(b(' ')) # deletion flag
for (fieldName, fieldType, size, dec), value in zip(self.fields, record):
fieldType = fieldType.upper()
size = int(size)
if fieldType.upper() == "N":
value = str(value).rjust(size)
elif fieldType == 'L':
value = str(value)[0].upper()
else:
value = str(value)[:size].ljust(size)
if len(value) != size:
raise ShapefileException(
"Shapefile Writer unable to pack incorrect sized value"
" (size %d) into field '%s' (size %d)." % (len(value), fieldName, size))
value = b(value)
f.write(value)
def null(self):
"""Creates a null shape."""
self._shapes.append(_Shape(NULL))
def point(self, x, y, z=0, m=0):
"""Creates a point shape."""
pointShape = _Shape(self.shapeType)
pointShape.points.append([x, y, z, m])
self._shapes.append(pointShape)
def line(self, parts=[], shapeType=POLYLINE):
"""Creates a line shape. This method is just a convienience method
which wraps 'poly()'.
"""
self.poly(parts, shapeType, [])
def poly(self, parts=[], shapeType=POLYGON, partTypes=[]):
"""Creates a shape that has multiple collections of points (parts)
including lines, polygons, and even multipoint shapes. If no shape type
is specified it defaults to 'polygon'. If no part types are specified
(which they normally won't be) then all parts default to the shape type.
"""
polyShape = _Shape(shapeType)
polyShape.parts = []
polyShape.points = []
# Make sure polygons are closed
if shapeType in (5,15,25,31):
for part in parts:
if part[0] != part[-1]:
part.append(part[0])
for part in parts:
polyShape.parts.append(len(polyShape.points))
for point in part:
# Ensure point is list
if not isinstance(point, list):
point = list(point)
# Make sure point has z and m values
while len(point) < 4:
point.append(0)
polyShape.points.append(point)
if polyShape.shapeType == 31:
if not partTypes:
for part in parts:
partTypes.append(polyShape.shapeType)
polyShape.partTypes = partTypes
self._shapes.append(polyShape)
def field(self, name, fieldType="C", size="50", decimal=0):
"""Adds a dbf field descriptor to the shapefile."""
self.fields.append((name, fieldType, size, decimal))
def record(self, *recordList, **recordDict):
"""Creates a dbf attribute record. You can submit either a sequence of
field values or keyword arguments of field names and values. Before
adding records you must add fields for the record values using the
fields() method. If the record values exceed the number of fields the
extra ones won't be added. In the case of using keyword arguments to specify
field/value pairs only fields matching the already registered fields
will be added."""
record = []
fieldCount = len(self.fields)
# Compensate for deletion flag
if self.fields[0][0].startswith("Deletion"): fieldCount -= 1
if recordList:
[record.append(recordList[i]) for i in range(fieldCount)]
elif recordDict:
for field in self.fields:
if field[0] in recordDict:
val = recordDict[field[0]]
if val is None:
record.append("")
else:
record.append(val)
if record:
self.records.append(record)
def shape(self, i):
return self._shapes[i]
def shapes(self):
"""Return the current list of shapes."""
return self._shapes
def saveShp(self, target):
"""Save an shp file."""
if not hasattr(target, "write"):
target = os.path.splitext(target)[0] + '.shp'
if not self.shapeType:
self.shapeType = self._shapes[0].shapeType
self.shp = self.__getFileObj(target)
self.__shapefileHeader(self.shp, headerType='shp')
self.__shpRecords()
def saveShx(self, target):
"""Save an shx file."""
if not hasattr(target, "write"):
target = os.path.splitext(target)[0] + '.shx'
if not self.shapeType:
self.shapeType = self._shapes[0].shapeType
self.shx = self.__getFileObj(target)
self.__shapefileHeader(self.shx, headerType='shx')
self.__shxRecords()
def saveDbf(self, target):
"""Save a dbf file."""
if not hasattr(target, "write"):
target = os.path.splitext(target)[0] + '.dbf'
self.dbf = self.__getFileObj(target)
self.__dbfHeader()
self.__dbfRecords()
def save(self, target=None, shp=None, shx=None, dbf=None):
"""Save the shapefile data to three files or
three file-like objects. SHP and DBF files can also
be written exclusively using saveShp, saveShx, and saveDbf respectively.
If target is specified but not shp,shx, or dbf then the target path and
file name are used. If no options or specified, a unique base file name
is generated to save the files and the base file name is returned as a
string.
"""
# Create a unique file name if one is not defined
if shp:
self.saveShp(shp)
if shx:
self.saveShx(shx)
if dbf:
self.saveDbf(dbf)
elif not shp and not shx and not dbf:
generated = False
if not target:
temp = tempfile.NamedTemporaryFile(prefix="shapefile_",dir=os.getcwd())
target = temp.name
generated = True
self.saveShp(target)
self.shp.close()
self.saveShx(target)
self.shx.close()
self.saveDbf(target)
self.dbf.close()
if generated:
return target
class Editor(Writer):
def __init__(self, shapefile=None, shapeType=POINT, autoBalance=1):
self.autoBalance = autoBalance
if not shapefile:
Writer.__init__(self, shapeType)
elif is_string(shapefile):
base = os.path.splitext(shapefile)[0]
if os.path.isfile("%s.shp" % base):
r = Reader(base)
Writer.__init__(self, r.shapeType)
self._shapes = r.shapes()
self.fields = r.fields
self.records = r.records()
def select(self, expr):
"""Select one or more shapes (to be implemented)"""
# TODO: Implement expressions to select shapes.
pass
def delete(self, shape=None, part=None, point=None):
"""Deletes the specified part of any shape by specifying a shape
number, part number, or point number."""
# shape, part, point
if shape and part and point:
del self._shapes[shape][part][point]
# shape, part
elif shape and part and not point:
del self._shapes[shape][part]
# shape
elif shape and not part and not point:
del self._shapes[shape]
# point
elif not shape and not part and point:
for s in self._shapes:
if s.shapeType == 1:
del self._shapes[point]
else:
for part in s.parts:
del s[part][point]
# part, point
elif not shape and part and point:
for s in self._shapes:
del s[part][point]
# part
elif not shape and part and not point:
for s in self._shapes:
del s[part]
def point(self, x=None, y=None, z=None, m=None, shape=None, part=None, point=None, addr=None):
"""Creates/updates a point shape. The arguments allows
you to update a specific point by shape, part, point of any
shape type."""
# shape, part, point
if shape and part and point:
try: self._shapes[shape]
except IndexError: self._shapes.append([])
try: self._shapes[shape][part]
except IndexError: self._shapes[shape].append([])
try: self._shapes[shape][part][point]
except IndexError: self._shapes[shape][part].append([])
p = self._shapes[shape][part][point]
if x: p[0] = x
if y: p[1] = y
if z: p[2] = z
if m: p[3] = m
self._shapes[shape][part][point] = p
# shape, part
elif shape and part and not point:
try: self._shapes[shape]
except IndexError: self._shapes.append([])
try: self._shapes[shape][part]
except IndexError: self._shapes[shape].append([])
points = self._shapes[shape][part]
for i in range(len(points)):
p = points[i]
if x: p[0] = x
if y: p[1] = y
if z: p[2] = z
if m: p[3] = m
self._shapes[shape][part][i] = p
# shape
elif shape and not part and not point:
try: self._shapes[shape]
except IndexError: self._shapes.append([])
# point
# part
if addr:
shape, part, point = addr
self._shapes[shape][part][point] = [x, y, z, m]
else:
Writer.point(self, x, y, z, m)
if self.autoBalance:
self.balance()
def validate(self):
"""An optional method to try and validate the shapefile
as much as possible before writing it (not implemented)."""
#TODO: Implement validation method
pass
def balance(self):
"""Adds a corresponding empty attribute or null geometry record depending
on which type of record was created to make sure all three files
are in synch."""
if len(self.records) > len(self._shapes):
self.null()
elif len(self.records) < len(self._shapes):
self.record()
def __fieldNorm(self, fieldName):
"""Normalizes a dbf field name to fit within the spec and the
expectations of certain ESRI software."""
if len(fieldName) > 11: fieldName = fieldName[:11]
fieldName = fieldName.upper()
fieldName.replace(' ', '_')
# Begin Testing
def test():
import doctest
doctest.NORMALIZE_WHITESPACE = 1
doctest.testfile("README.txt", verbose=1)
if __name__ == "__main__":
"""
Doctests are contained in the file 'README.txt'. This library was originally developed
using Python 2.3. Python 2.4 and above have some excellent improvements in the built-in
testing libraries but for now unit testing is done using what's available in
2.3.
"""
test()
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