Python QgsFeature.changeAttribute方法代码示例

# 需要导入模块: from qgis.core import QgsFeature [as 别名]
# 或者: from qgis.core.QgsFeature import changeAttribute [as 别名]
 def test_ChangeAttribute(self):
     feat = QgsFeature()
     feat.addAttribute(1, "text")
     feat.changeAttribute(1, "changed")
     myChangedAttribute = feat.attributeMap()[1].toString()
     myExpectedAttribute = "changed"
     myMessage = '\nExpected: %s\nGot: %s' % (myExpectedAttribute, 
         myChangedAttribute)
     assert myChangedAttribute == myExpectedAttribute, myMessage        

# 需要导入模块: from qgis.core import QgsFeature [as 别名]
# 或者: from qgis.core.QgsFeature import changeAttribute [as 别名]

#.........这里部分代码省略.........
        myMessage = tr('Could not obtain data provider from '
                       'layer "%s"' % layer.source())
        raise Exception(myMessage)

    # Get the layer field list, select by our extent then write to disk
    # .. todo:: FIXME - for different geometry types we should implement
    #    different clipping behaviour e.g. reject polygons that
    #    intersect the edge of the bbox. Tim
    myAttributes = myProvider.attributeIndexes()
    myFetchGeometryFlag = True
    myUseIntersectFlag = True
    myProvider.select(
        myAttributes,
        myProjectedExtent,
        myFetchGeometryFlag,
        myUseIntersectFlag)

    myFieldList = myProvider.fields()

    myWriter = QgsVectorFileWriter(
        myFilename,
        'UTF-8',
        myFieldList,
        layer.wkbType(),
        myGeoCrs,
        #'SQLite')  # FIXME (Ole): This works but is far too slow
        'ESRI Shapefile')
    if myWriter.hasError() != QgsVectorFileWriter.NoError:
        myMessage = tr('Error when creating shapefile: <br>Filename:'
                       '%s<br>Error: %s' %
                       (myFilename, myWriter.hasError()))
        raise Exception(myMessage)

    # Reverse the coordinate xform now so that we can convert
    # geometries from layer crs to geocrs.
    myXForm = QgsCoordinateTransform(layer.crs(), myGeoCrs)
    # Retrieve every feature with its geometry and attributes
    myFeature = QgsFeature()
    myCount = 0
    myHasMultipart = False

    if explode_attribute is not None:
        theExplodeAttributeIndex = myProvider.fieldNameIndex(
            explode_attribute)

    while myProvider.nextFeature(myFeature):
        myGeometry = myFeature.geometry()
        if explode_attribute is not None:
            myAttrs = myFeature.attributeMap()
        # Loop through the parts adding them to the output file
        # we write out single part features unless explode_flag is False
        if explode_flag:
            myGeometryList = explode_multipart_geometry(myGeometry)
        else:
            myGeometryList = [myGeometry]

        for myPartIndex, myPart in enumerate(myGeometryList):
            myPart.transform(myXForm)
            if hard_clip_flag:
                # Remove any dangling bits so only intersecting area is
                # kept.
                myPart = clip_geometry(myClipPolygon, myPart)
            if myPart is None:
                continue

            myFeature.setGeometry(myPart)
            # There are multiple parts and we want to show it in the
            # explode_attribute
            if myPartIndex > 0 and explode_attribute is not None:
                myHasMultipart = True
                myPartAttr = QVariant(
                    '%s #%s' % (myAttrs[theExplodeAttributeIndex].toString(),
                                myPartIndex))
                myFeature.changeAttribute(theExplodeAttributeIndex, myPartAttr)

            myWriter.addFeature(myFeature)
        myCount += 1
    del myWriter  # Flush to disk

    if myCount < 1:
        myMessage = tr(
            'No features fall within the clip extents. Try panning / zooming '
            'to an area containing data and then try to run your analysis '
            'again. If hazard and exposure data doesn\'t overlap at all, it '
            'is not possible to do an analysis. Another possibility is that '
            'the layers do overlap but because they may have different '
            'spatial references, they appear to be disjointed. If this is the '
            'case, try to turn on reproject on-the-fly in QGIS.')
        raise NoFeaturesInExtentError(myMessage)

    myKeywordIO = KeywordIO()
    if extra_keywords is None:
        extra_keywords = {}
    extra_keywords['HAD_MULTIPART_POLY'] = myHasMultipart
    myKeywordIO.copy_keywords(
        layer, myFilename, extra_keywords=extra_keywords)
    myBaseName = '%s clipped' % layer.name()
    myLayer = QgsVectorLayer(myFilename, myBaseName, 'ogr')

    return myLayer