254 lines
6.7 KiB
Python
254 lines
6.7 KiB
Python
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from ctypes import byref, c_int
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from datetime import date, datetime, time
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from django.contrib.gis.gdal.base import GDALBase
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from django.contrib.gis.gdal.error import GDALException
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from django.contrib.gis.gdal.prototypes import ds as capi
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from django.utils.encoding import force_str
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# For more information, see the OGR C API source code:
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# https://gdal.org/api/vector_c_api.html
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#
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# The OGR_Fld_* routines are relevant here.
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class Field(GDALBase):
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"""
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Wrap an OGR Field. Needs to be instantiated from a Feature object.
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"""
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def __init__(self, feat, index):
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"""
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Initialize on the feature object and the integer index of
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the field within the feature.
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"""
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# Setting the feature pointer and index.
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self._feat = feat
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self._index = index
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# Getting the pointer for this field.
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fld_ptr = capi.get_feat_field_defn(feat.ptr, index)
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if not fld_ptr:
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raise GDALException("Cannot create OGR Field, invalid pointer given.")
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self.ptr = fld_ptr
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# Setting the class depending upon the OGR Field Type (OFT)
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self.__class__ = OGRFieldTypes[self.type]
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def __str__(self):
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"Return the string representation of the Field."
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return str(self.value).strip()
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# #### Field Methods ####
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def as_double(self):
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"Retrieve the Field's value as a double (float)."
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return (
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capi.get_field_as_double(self._feat.ptr, self._index)
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if self.is_set
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else None
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)
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def as_int(self, is_64=False):
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"Retrieve the Field's value as an integer."
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if is_64:
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return (
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capi.get_field_as_integer64(self._feat.ptr, self._index)
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if self.is_set
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else None
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)
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else:
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return (
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capi.get_field_as_integer(self._feat.ptr, self._index)
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if self.is_set
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else None
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)
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def as_string(self):
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"Retrieve the Field's value as a string."
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if not self.is_set:
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return None
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string = capi.get_field_as_string(self._feat.ptr, self._index)
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return force_str(string, encoding=self._feat.encoding, strings_only=True)
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def as_datetime(self):
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"Retrieve the Field's value as a tuple of date & time components."
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if not self.is_set:
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return None
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yy, mm, dd, hh, mn, ss, tz = [c_int() for i in range(7)]
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status = capi.get_field_as_datetime(
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self._feat.ptr,
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self._index,
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byref(yy),
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byref(mm),
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byref(dd),
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byref(hh),
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byref(mn),
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byref(ss),
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byref(tz),
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)
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if status:
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return (yy, mm, dd, hh, mn, ss, tz)
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else:
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raise GDALException(
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"Unable to retrieve date & time information from the field."
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)
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# #### Field Properties ####
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@property
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def is_set(self):
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"Return True if the value of this field isn't null, False otherwise."
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return capi.is_field_set(self._feat.ptr, self._index)
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@property
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def name(self):
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"Return the name of this Field."
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name = capi.get_field_name(self.ptr)
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return force_str(name, encoding=self._feat.encoding, strings_only=True)
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@property
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def precision(self):
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"Return the precision of this Field."
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return capi.get_field_precision(self.ptr)
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@property
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def type(self):
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"Return the OGR type of this Field."
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return capi.get_field_type(self.ptr)
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@property
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def type_name(self):
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"Return the OGR field type name for this Field."
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return capi.get_field_type_name(self.type)
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@property
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def value(self):
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"Return the value of this Field."
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# Default is to get the field as a string.
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return self.as_string()
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@property
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def width(self):
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"Return the width of this Field."
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return capi.get_field_width(self.ptr)
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# ### The Field sub-classes for each OGR Field type. ###
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class OFTInteger(Field):
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_bit64 = False
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@property
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def value(self):
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"Return an integer contained in this field."
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return self.as_int(self._bit64)
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@property
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def type(self):
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"""
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GDAL uses OFTReals to represent OFTIntegers in created
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shapefiles -- forcing the type here since the underlying field
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type may actually be OFTReal.
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"""
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return 0
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class OFTReal(Field):
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@property
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def value(self):
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"Return a float contained in this field."
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return self.as_double()
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# String & Binary fields, just subclasses
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class OFTString(Field):
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pass
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class OFTWideString(Field):
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pass
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class OFTBinary(Field):
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pass
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# OFTDate, OFTTime, OFTDateTime fields.
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class OFTDate(Field):
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@property
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def value(self):
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"Return a Python `date` object for the OFTDate field."
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try:
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yy, mm, dd, hh, mn, ss, tz = self.as_datetime()
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return date(yy.value, mm.value, dd.value)
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except (TypeError, ValueError, GDALException):
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return None
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class OFTDateTime(Field):
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@property
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def value(self):
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"Return a Python `datetime` object for this OFTDateTime field."
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# TODO: Adapt timezone information.
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# See https://lists.osgeo.org/pipermail/gdal-dev/2006-February/007990.html
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# The `tz` variable has values of: 0=unknown, 1=localtime (ambiguous),
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# 100=GMT, 104=GMT+1, 80=GMT-5, etc.
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try:
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yy, mm, dd, hh, mn, ss, tz = self.as_datetime()
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return datetime(yy.value, mm.value, dd.value, hh.value, mn.value, ss.value)
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except (TypeError, ValueError, GDALException):
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return None
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class OFTTime(Field):
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@property
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def value(self):
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"Return a Python `time` object for this OFTTime field."
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try:
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yy, mm, dd, hh, mn, ss, tz = self.as_datetime()
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return time(hh.value, mn.value, ss.value)
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except (ValueError, GDALException):
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return None
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class OFTInteger64(OFTInteger):
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_bit64 = True
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# List fields are also just subclasses
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class OFTIntegerList(Field):
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pass
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class OFTRealList(Field):
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pass
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class OFTStringList(Field):
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pass
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class OFTWideStringList(Field):
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pass
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class OFTInteger64List(Field):
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pass
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# Class mapping dictionary for OFT Types and reverse mapping.
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OGRFieldTypes = {
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0: OFTInteger,
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1: OFTIntegerList,
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2: OFTReal,
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3: OFTRealList,
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4: OFTString,
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5: OFTStringList,
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6: OFTWideString,
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7: OFTWideStringList,
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8: OFTBinary,
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9: OFTDate,
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10: OFTTime,
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11: OFTDateTime,
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12: OFTInteger64,
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13: OFTInteger64List,
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}
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ROGRFieldTypes = {cls: num for num, cls in OGRFieldTypes.items()}
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