[英]How to remove all layers *except* some specific ones in pyqgis?
我需要为我的 QGIS 项目加载几个矢量图层,以便我在每个矢量图层中测试我的脚本的每个功能。 但是,最后我只想处理一两层感兴趣的层而丢弃其他层,所以我想自动执行此操作。
我在一些层上成功地做到了这一点,但是有一层给我带来了问题,我还没有弄清楚原因。
这是一些代码:
加载层(这些几乎肯定不是问题):
a2 = iface.addVectorLayer(path + ardida2, "", "ogr")
if not a2:
print("Layer failed to load!")
a3 = iface.addVectorLayer(path + ardida3, "", "ogr")
if not a3:
print("Layer failed to load!")
现在这是我创建的函数,用于删除所有加载的图层,除了我想要使用的图层。 prints
地方只是因为我试图理解这个问题。
def RemoveAllLayersExcept(*layers):
layer_ids = []
for l in layers:
layer_ids.append(l.id())
print('layer_ids', layer_ids)
for lyr in QgsProject.instance().mapLayers():
print(lyr)
if lyr not in layer_ids:
print('not')
QgsProject.instance().removeMapLayer(lyr)
else:
pass
然后我创建了一个新层——那个给我带来了问题的层。 稍后我需要在迭代过程中编辑此图层。 我在名为PyQGIS: Create a Shapefile 的OpenSourceOptions 教程中遵循了一个分步示例:
# OPENSOURCEOPTIONS TUTORIAL - PYQGIS: Create a Shapefile
# create fields
layerFields = QgsFields()
layerFields.append(QgsField('ID', QVariant.Int))
layerFields.append(QgsField('Value', QVariant.Double))
layerFields.append(QgsField('Name', QVariant.String))
# Now define the file path for the new shapefile
# Note: the CRS used here is NAD 1983 UTM Zone 11 N
fn = 'D:/Sara/Trabalho/QGIS/pnogas/fireball_points.shp'
writer = QgsVectorFileWriter(fn, 'UTF-8', layerFields, QgsWkbTypes.Point,QgsCoordinateReferenceSystem('EPSG:26912'), 'ESRI Shapefile')
# For each feature we need to set the geometry (in this case a point)
# set the attribute values, then add it to the vector layer.
feat = QgsFeature() # create an empty QgsFeature()
feat.setGeometry(QgsGeometry.fromPointXY(QgsPointXY(cx14, cy14))) # create a point and use it to set the feature geometry
feat.setAttributes([1, 1.1, 'one']) # set the attribute values
writer.addFeature(feat) # add the feature to the layer
layer_fireball = iface.addVectorLayer(fn, '', 'ogr')
if not layer_fireball:
print("Layer failed to load!")
del(writer)
然后我删除我不感兴趣的图层:
RemoveAllLayersExcept(layer, layer_fireball)
就是这样。 当我第一次运行程序时,没有任何反应。 这是我得到的:
layer_ids ['COS2018_ardida2018_3_clip_cbf56f4b_e668_4c2e_9259_7d22d5943097', 'fireball_points_f92b32e0_f8bf_42c1_95e6_b317ddf6ee84']
COS2018_ardida2018_2_clip_45b241c4_fb9b_4654_9916_5ff08514c559
not
COS2018_ardida2018_3_clip_cbf56f4b_e668_4c2e_9259_7d22d5943097
fireball_points_f92b32e0_f8bf_42c1_95e6_b317ddf6ee84
这符合我的预期。 但在第二次和第 n 次,我得到:
Layer failed to load!
Traceback (most recent call last):
File "C:\PROGRA~1\QGIS3~1.10\apps\Python37\lib\code.py", line 90, in runcode
exec(code, self.locals)
File "<input>", line 1, in <module>
File "<string>", line 676, in <module>
File "<string>", line 104, in RemoveAllLayersExcept
AttributeError: 'NoneType' object has no attribute 'id'
你能发现问题出在哪里吗? 为什么会出现这个错误? 为什么它只从第二次运行开始?
谢谢!
更改RemoveAllLayersExcept
方法,如下所示:
def RemoveAllLayersExcept(*keep_layers):
layers = QgsProject.instance().mapLayers().values()
will_be_deleted = [l for l in layers if l not in keep_layers]
for layer in will_be_deleted:
QgsProject.instance().removeMapLayer(layer)
声明:本站的技术帖子网页,遵循CC BY-SA 4.0协议,如果您需要转载,请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.