/django/contrib/gis/gdal/field.py
https://code.google.com/p/mango-py/ · Python · 186 lines · 128 code · 26 blank · 32 comment · 15 complexity · 1c97e6b9e0cd031036ba9cf75e5e4eea MD5 · raw file
- from ctypes import byref, c_int
- from datetime import date, datetime, time
- from django.contrib.gis.gdal.base import GDALBase
- from django.contrib.gis.gdal.error import OGRException
- from django.contrib.gis.gdal.prototypes import ds as capi
- # For more information, see the OGR C API source code:
- # http://www.gdal.org/ogr/ogr__api_8h.html
- #
- # The OGR_Fld_* routines are relevant here.
- class Field(GDALBase):
- "A class that wraps an OGR Field, needs to be instantiated from a Feature object."
- #### Python 'magic' routines ####
- def __init__(self, feat, index):
- """
- Initializes on the feature pointer and the integer index of
- the field within the feature.
- """
- # Setting the feature pointer and index.
- self._feat = feat
- self._index = index
- # Getting the pointer for this field.
- fld_ptr = capi.get_feat_field_defn(feat, index)
- if not fld_ptr:
- raise OGRException('Cannot create OGR Field, invalid pointer given.')
- self.ptr = fld_ptr
- # Setting the class depending upon the OGR Field Type (OFT)
- self.__class__ = OGRFieldTypes[self.type]
- # OFTReal with no precision should be an OFTInteger.
- if isinstance(self, OFTReal) and self.precision == 0:
- self.__class__ = OFTInteger
- self._double = True
- def __str__(self):
- "Returns the string representation of the Field."
- return str(self.value).strip()
- #### Field Methods ####
- def as_double(self):
- "Retrieves the Field's value as a double (float)."
- return capi.get_field_as_double(self._feat, self._index)
- def as_int(self):
- "Retrieves the Field's value as an integer."
- return capi.get_field_as_integer(self._feat, self._index)
- def as_string(self):
- "Retrieves the Field's value as a string."
- return capi.get_field_as_string(self._feat, self._index)
- def as_datetime(self):
- "Retrieves the Field's value as a tuple of date & time components."
- yy, mm, dd, hh, mn, ss, tz = [c_int() for i in range(7)]
- status = capi.get_field_as_datetime(self._feat, self._index, byref(yy), byref(mm), byref(dd),
- byref(hh), byref(mn), byref(ss), byref(tz))
- if status:
- return (yy, mm, dd, hh, mn, ss, tz)
- else:
- raise OGRException('Unable to retrieve date & time information from the field.')
- #### Field Properties ####
- @property
- def name(self):
- "Returns the name of this Field."
- return capi.get_field_name(self.ptr)
- @property
- def precision(self):
- "Returns the precision of this Field."
- return capi.get_field_precision(self.ptr)
- @property
- def type(self):
- "Returns the OGR type of this Field."
- return capi.get_field_type(self.ptr)
- @property
- def type_name(self):
- "Return the OGR field type name for this Field."
- return capi.get_field_type_name(self.type)
- @property
- def value(self):
- "Returns the value of this Field."
- # Default is to get the field as a string.
- return self.as_string()
- @property
- def width(self):
- "Returns the width of this Field."
- return capi.get_field_width(self.ptr)
- ### The Field sub-classes for each OGR Field type. ###
- class OFTInteger(Field):
- _double = False
- @property
- def value(self):
- "Returns an integer contained in this field."
- if self._double:
- # If this is really from an OFTReal field with no precision,
- # read as a double and cast as Python int (to prevent overflow).
- return int(self.as_double())
- else:
- return self.as_int()
- @property
- def type(self):
- """
- GDAL uses OFTReals to represent OFTIntegers in created
- shapefiles -- forcing the type here since the underlying field
- type may actually be OFTReal.
- """
- return 0
- class OFTReal(Field):
- @property
- def value(self):
- "Returns a float contained in this field."
- return self.as_double()
- # String & Binary fields, just subclasses
- class OFTString(Field): pass
- class OFTWideString(Field): pass
- class OFTBinary(Field): pass
- # OFTDate, OFTTime, OFTDateTime fields.
- class OFTDate(Field):
- @property
- def value(self):
- "Returns a Python `date` object for the OFTDate field."
- try:
- yy, mm, dd, hh, mn, ss, tz = self.as_datetime()
- return date(yy.value, mm.value, dd.value)
- except (ValueError, OGRException):
- return None
- class OFTDateTime(Field):
- @property
- def value(self):
- "Returns a Python `datetime` object for this OFTDateTime field."
- # TODO: Adapt timezone information.
- # See http://lists.maptools.org/pipermail/gdal-dev/2006-February/007990.html
- # The `tz` variable has values of: 0=unknown, 1=localtime (ambiguous),
- # 100=GMT, 104=GMT+1, 80=GMT-5, etc.
- try:
- yy, mm, dd, hh, mn, ss, tz = self.as_datetime()
- return datetime(yy.value, mm.value, dd.value, hh.value, mn.value, ss.value)
- except (ValueError, OGRException):
- return None
- class OFTTime(Field):
- @property
- def value(self):
- "Returns a Python `time` object for this OFTTime field."
- try:
- yy, mm, dd, hh, mn, ss, tz = self.as_datetime()
- return time(hh.value, mn.value, ss.value)
- except (ValueError, OGRException):
- return None
- # List fields are also just subclasses
- class OFTIntegerList(Field): pass
- class OFTRealList(Field): pass
- class OFTStringList(Field): pass
- class OFTWideStringList(Field): pass
- # Class mapping dictionary for OFT Types and reverse mapping.
- OGRFieldTypes = { 0 : OFTInteger,
- 1 : OFTIntegerList,
- 2 : OFTReal,
- 3 : OFTRealList,
- 4 : OFTString,
- 5 : OFTStringList,
- 6 : OFTWideString,
- 7 : OFTWideStringList,
- 8 : OFTBinary,
- 9 : OFTDate,
- 10 : OFTTime,
- 11 : OFTDateTime,
- }
- ROGRFieldTypes = dict([(cls, num) for num, cls in OGRFieldTypes.items()])