在 ogr 或 geopandas python

问题描述

我需要来自 shapefile 的 FID 列的信息。不知何故，当您加载 shapefile 时，该列不会“显示”。我需要该列的信息，因为我需要说：

fid	id	标签
1	1	森林
2	1	森林
3	2	水
4	2	水
5	3	城市

我需要知道哪些 fids 属于 ids X、Y、Z 等。我在 geopandas 中尝试了以下内容。使用 osgeo 的 geopandas 或 OGR 是否有更有效的方法？谢谢

import os
import geopandas as gpd
import numpy as np
from osgeo import ogr

# open the training data
train_cl_fn = os.path.join(src,"train.shp")

# read the column "id" that already exists. This id column says that feature X belongs to id Y
X_train_G = gpd.read_file(train_cl_fn)
class_ids = X_train_G["id"].unique()
print('class ids: ',class_ids)

# I create an empty array for the fids
class_fids = np.array([])
print('class labels: ',class_fids)

# add "fidl" column,using "id" and the empty array
# FID and fid are the same,therefore "fidl"
X_train_G['fidl'] = X_train_G['id'].map(dict(zip(class_ids,class_fids)))
print(X_train_G.head())

# export: rewrite file
X_train_G.to_file(os.path.join(src,"train.shp"))

# open the SAME file again,this time in ogr
train_cl_fn = os.path.join(src,"train.shp")
driver = ogr.GetDriverByName('ESRI Shapefile')
train_ds = driver.Open(train_cl_fn,1) # 0 means read-only. 1 means writeable.
layer = train_ds.GetLayer()

for Ft in layer:
    ThisID = int(Ft.GetFID())
    #print('id is {}'.format(ThisID))
    Ft.SetField('fidl',ThisID)          # Write the FID to the fidl field
    layer.SetFeature(Ft)              # update the feature
dataSource = None  # save/rewrite file with fid info in the fidl column

解决方法

好的……阅读了一些之后，我找到了一种更有效的方法。

import os
from osgeo import ogr

src = "C:/path/"

#### Read SHP and create X_train_x segments array ####
# open training data
train_cl_fn = os.path.join(src,"train.shp")
driver = ogr.GetDriverByName('ESRI Shapefile')
train_ds = driver.Open(train_cl_fn,1) # 0 means read-only. 1 means writeable.
layer = train_ds.GetLayer()

fieldDefn = ogr.FieldDefn('fidl',ogr.OFTReal) 
fieldDefn.SetWidth(14) 
fieldDefn.SetPrecision(6)
layer.CreateField(fieldDefn)

for Ft in layer:
    ThisID = int(Ft.GetFID())
    #print('id is {}'.format(ThisID))
    Ft.SetField('fidl',ThisID)          # Write the FID to the fidl field
    layer.SetFeature(Ft)              # update the feature
dataSource = None  

你知道一种更好的方法吗？