Question

答案：感谢@ nils-werner和@goyo指出我正确的方向：我需要传递Move iterTwo = layerTwo.getFeatures() right before for feat in iterTwo :：

layerOne = QgsVectorLayer( '~/FirstLayer.shp', 'layerOne', 'ogr')
layerTwo = QgsVectorLayer( '~/SecondLayer.shp', 'layerTwo', 'ogr')

iterOne = layerOne.getFeatures()

for feature in iterOne: 
    layerOneId = feature.attributes()[0]
    print layerOneId
    iterTwo = layerTwo.getFeatures()
    for feat in iterTwo :
        layerTwoId = feat.attributes()[0]
        print "LayerOneId",LayerOneId, "LayerTwoId", LayerTwoId"
        # do something if LayerOneId == LayerTwoId

我有两层，我想比较一下：

layerOne = QgsVectorLayer( '~/FirstLayer.shp', 'layerOne', 'ogr')
layerTwo = QgsVectorLayer( '~/SecondLayer.shp', 'layerTwo', 'ogr')

iterOne = layerOne.getFeatures()
iterTwo = layerTwo.getFeatures()
for feature in iterOne: 
    layerOneId = feature.attributes()[0]
    print layerOneId
    for feat in iterTwo :
        layerTwoId = feat.attributes()[0]
        print "LayerOneId",LayerOneId, "LayerTwoId", LayerTwoId"
        # do something if LayerOneId == LayerTwoId

此代码在LayerOne的第一次迭代中正确运行，但随后仅在第一层上进行迭代而不检查第二层。结果如下：

LayerOneId, 0

LayerOneId, 0, LayerTwoId, 0

LayerOneId, 0, LayerTwoId, 1

...

LayerOneId, 0, LayerTwoId, n

LayerOneId, 1

LayerOneId, 2

...

LayerOneId, n

为什么我的函数只迭代第一层的第一个特征？

更准确地说，我正在寻找一个在python控制台中运行的结果：

arrayOne = [1,2]
arrayTwo = [1,2]
for a in arrayOne :
    for b in arrayTwo:
        print a,b
>>> 1,1
>>> 1,2
>>> 2,1
>>> 2,2

Answer 1

我会使用itertools.product来迭代这两个功能

import itertools

layerOne = QgsVectorLayer( '~/FirstLayer.shp', 'layerOne', 'ogr')
layerTwo = QgsVectorLayer( '~/SecondLayer.shp', 'layerTwo', 'ogr')

for features in itertools.product(layerOne.getFeatures(), layerTwo.getFeatures()):

    id = tuple(feat.attributes()[0] for feat in features)

    print "LayerOneId" ,id[0] , "LayerTwoId", id[1]

    if id[0] == id[1]:
        pass
        # code if both id's match

features是具有两个图层功能的元组。如果您需要除ID以外的更多功能，则可以使用zipped_attributes = zip(*feat.attributes() for feat in features)之类的内容对其进行转置，并使用id = zipped_attributes[0]

访问带有ID的元组

Answer 2

答案：感谢@ nils-werner和@goyo指出我正确的方向：我需要在Move iterTwo = layerTwo.getFeatures()之前通过feat in iterTwo :，因此：

layerOne = QgsVectorLayer( '~/FirstLayer.shp', 'layerOne', 'ogr')
layerTwo = QgsVectorLayer( '~/SecondLayer.shp', 'layerTwo', 'ogr')

iterOne = layerOne.getFeatures()

for feature in iterOne: 
    layerOneId = feature.attributes()[0]
    print layerOneId
    iterTwo = layerTwo.getFeatures()
    for feat in iterTwo :
        layerTwoId = feat.attributes()[0]
        print "LayerOneId",LayerOneId, "LayerTwoId", LayerTwoId"
        # do something if LayerOneId == LayerTwoId

如何迭代两个不同qgis图层的要素？

2 个答案: