打开QGIS Desktop 3.22.16，加载一个矢量图（Ex48/area.shp）
激活当前矢量图层

layer=iface.activeLayer()

 

 获取当前矢量图层矢量数据的个数

from qgis.utils import iface

layer = iface.activeLayer()  # 得到当前激活的图层
print(layer.id())
print(layer.featureCount())  # 返回矢量图层特征的数量

 

访问图层中的某一个要素

layer = iface.activeLayer()

for feat in layer.getFeatures():
    geom=feat.geometry()
    print(type(geom))
    print(geom.asWkt()[:10],geom.area(),geom.length())

 通过id访问要素

print('the layer has {} features.'.format(layer.featureCount()))
feat = layer.getFeature(10)  # id < featureCount
print(feat.id())
print(feat.isValid())  # return true

检查id是否有效：id要小于要素个数

 得到要素的属性信息

attr = feat1.attributes()

 提取多边形节点

vertices = list(geom.vertices())

 显示节点

def getgtypes():
    return 'point', 'linestring', 'polygon', 'multipoint', 'multilinestring', 'multipolygon'


def showgeoms(geoms, name="tmp", gtype=None):
    # 快速显示一串几何对象,gtype 如果是默认的则根据geoms生成相应的类型
    if gtype is None:
        gtype = geoms[0].constGet().geometryType() if isinstance(geoms[0], QgsGeometry) else geoms[0].geometryType()
        gtype = gtype.lower()
    if gtype not in getgtypes():
        raise Exception('gtype should be one of :{' + ','.join(getgtypes()) + '}' + 'input gtype is {}'.format(gtype))
    vl = QgsVectorLayer(gtype, name, "memory")
    pr = vl.dataProvider()
    feats = []
    for geom in geoms:
        feat = QgsFeature()
        feat.setGeometry(geom)
        feats.append(feat)
    pr.addFeatures(feats)
    QgsProject.instance().addMapLayer(vl)
    iface.zoomFull()

layer = iface.activeLayer()
feat = layer.getFeature(12) 
geom = feat.geometry()   
vertices = list(geom.vertices())
showgeoms(vertices, 'feat12')

上面的代码运行时没有效果。。。

参考：矢量图层中要素的几何特征和属性特征的访问​​​​​​​