类型错误：'NoneType'对象不可迭代。(arcpy.ListFeatureClasses)

Question

我正在尝试将任何未知的投影形状文件更改为 “NAD 1983阿拉斯加阿尔伯斯”预测。在

# import arcypy and from arcpy, import os to change directory
import arcpy
from arcpy import os

# set working directory to workspace 
os.chdir('C://Users/Elvis/Desktop/Spring/Geog376/Lab03/erase')

# Copy all dataset in working directory ###Need to change this back into my s drive
arcpy.CopyFeatures_management('C://Users/Elvis/Desktop/Spring/Geog376/Lab03/lab03_data/2004  _af.shp','C://Users/Elvis/Desktop/Spring/Geog376/Lab03/erase/2004_af.shp')
arcpy.CopyFeatures_management('C://Users/Elvis/Desktop/Spring/Geog376/Lab03/lab03_data/2004perimeters.shp','C://Users/Elvis/Desktop/Spring/Geog376/Lab03/erase/2004perimeters.shp')
arcpy.CopyFeatures_management('C://Users/Elvis/Desktop/Spring/Geog376/Lab03/lab03_data/AK_tundra.shp','C://Users/Elvis/Desktop/Spring/Geog376/Lab03/erase/AK_tundra.shp')
arcpy.CopyFeatures_management('C://Users/Elvis/Desktop/Spring/Geog376/Lab03/lab03_data/AK_taiga.shp','C://Users/Elvis/Desktop/Spring/Geog376/Lab03/erase/AK_taiga.shp')

# find what projection 2004_af.shp, 2004perimets.shp, AK_tundra, and AK_taiga.shp
# change the projections to the correct one (2004_af.shp)

# 2004_af.shp
desc_af =      arcpy.Describe('C://Users/Elvis/Desktop/Spring/Geog376/Lab03/erase/2004_af.shp')
sr_af = desc_af.spatialReference
print "projection name: "+sr_af.PCSname


# 2004perimeters.shp
desc_perimeters =    arcpy.Describe('C://Users/Elvis/Desktop/Spring/Geog376/Lab03/erase/2004perimeters.shp')
sr_perimeters = desc_perimeters.spatialReference
print "projection name: "+sr_perimeters.PCSname

# AK_tundra.shp
desc_tundra = arcpy.Describe('C://Users/Elvis/Desktop/Spring/Geog376/Lab03/erase/AK_tundra.shp')
sr_tundra = desc_tundra.spatialReference
print "projection name: "+sr_tundra.PCSname

# AK_taiga.shp
desc_taiga = arcpy.Describe('C://Users/Elvis/Desktop/Spring/Geog376/Lab03/erase/AK_taiga.shp')
sr_taiga = desc_taiga.spatialReference
print "projection name: "+sr_taiga.PCSname


# Here is where I got an error: arcpy.ListFeatureClasses

for infc in arcpy.ListFeatureClasses('2004perimeters', 'AK_tundra', 'AK_taiga'):
    desc = arcpy.Describe(infc)
    if desc.spatialReference.PCSname == "Unknown":
        outfc = os.path.join('C://Users/Elvis/Desktop/Spring/Geog376/Lab03/erase', infc) 
        # Set output coordinate system
        outcs = arcpy.SpatialReference('NAD 1983 Alaska Albers')
        # run project tool
        arcpy.Project_management(arcpy.ListFeatureClasses(infc, outfc, outcs))
        # check messages
        print arcpy.GetMessages()

Answer 1

函数arcpy.ListFeatureClasses()提供当前工作区中所有要素类的列表（您可以使用arcpy.env.工作区). 它不需要任何参数，除非您想用通配符、要素类型或特定的地理数据库要素数据集过滤结果。如果引用help，您将看到传递给ListFeatureClasses的参数与它的参数不一致。这就是为什么它返回None，而你的for语句不能在None上迭代。如果您不需要进行任何筛选，则可以：

arcpy.env.workspace = 'C:/Users/Elvis/Desktop/Spring/Geog376/Lab03/erase'
for infc in arcpy.ListFeatureClasses():

如果您只想迭代三个特定的数据集，那么只需显式地设置它们（您仍然可以使用工作区环境来避免键入完整的路径名）：

^{pr2}$

ListFeatureClasses函数也不属于对Project的调用中。此外，项目工具似乎并不是您所需要的。“项目”工具将数据从一个坐标系投影到另一个坐标系。相反，请看一下Define Projection工具。在