Python子过程公式

Question

我一直在试验Python的子流程模块。我希望效仿以下成功的指挥：

命令行：

ogr2ogr -f GeoJSON -clipsrc cutting.json output.json input.json

Python实现：

import subprocess
subprocess.call(["ogr2ogr", "-f", "GeoJSON", "-clipsrc", "cutting.json", "output.json", "input.json"], shell=True)

但是，python脚本输出：FAILURE: no target datasource provided

从文档中，我可以看到语法是正确的，并且我以正确的顺序指定了源数据源和目标数据源。当然，由于它在命令行上工作，所以我倾向于认为数据方向是正确的。我是不是不正确地调用子进程？

作为参考，ogr2ogr的使用：

Usage: ogr2ogr [--help-general] [-skipfailures] [-append] [-update]
               [-select field_list] [-where restricted_where]
               [-progress] [-sql <sql statement>] [-dialect dialect]
               [-preserve_fid] [-fid FID]
               [-spat xmin ymin xmax ymax] [-geomfield field]
               [-a_srs srs_def] [-t_srs srs_def] [-s_srs srs_def]
               [-f format_name] [-overwrite] [[-dsco NAME=VALUE] ...]
               dst_datasource_name src_datasource_name
               [-lco NAME=VALUE] [-nln name] [-nlt type] [-dim 2|3|layer_dim] [layer [layer ...]]

Advanced options :
               [-gt n]
               [-clipsrc [xmin ymin xmax ymax]|WKT|datasource|spat_extent]
               [-clipsrcsql sql_statement] [-clipsrclayer layer]
               [-clipsrcwhere expression]
               [-clipdst [xmin ymin xmax ymax]|WKT|datasource]
               [-clipdstsql sql_statement] [-clipdstlayer layer]
               [-clipdstwhere expression]
               [-wrapdateline][-datelineoffset val]
               [[-simplify tolerance] | [-segmentize max_dist]]
               [-addfields]
               [-relaxedFieldNameMatch]
               [-fieldTypeToString All|(type1[,type2]*)] [-unsetFieldWidth]
               [-fieldmap identity | index1[,index2]*]
               [-splitlistfields] [-maxsubfields val]
               [-explodecollections] [-zfield field_name]
               [-gcp pixel line easting northing [elevation]]* [-order n | -tps]

Answer 1

就我个人而言，我在基于*nix的机器上使用如下所示的内容来完全发送python脚本中的调用。也许它对你有帮助(或者你可以根据你的需要量身定做)。

import os, subprocess, time
name = 'ogr2ogr_{}'.format(time.time())
call = ['nohup', 'ogr2ogr', '-f', 'GeoJSON', '-clipsrc', 
        'cutting.json', 'output.json', 'input.json']
o_std = open(os.path.join('/my/log/dir', '{}.log'.format(name)), 'w')
o_err = open(os.path.join('/my/log/dir', '{}.err'.format(name)), 'w')
r = subprocess.Popen(call, stdout=o_std, stderr=o_err, preexec_fn=os.setpgrp)

如果不想分派子进程，只需删除nohup列表项，不要将os.setpgrp设置为preexec_fn。

Answer 2

我通常使用子进程来调用命令行，对于ogr2ogr，我可以通过在调用中添加shell=True选项来工作：

ProcessToCall = ['ogr2ogr'+" "+str(OutShp)+" "+str(InShp)+" "+'-dialect sqlite -sql "SELECT ST_Union(geometry) AS geometry FROM'+" "+str(InShp).split(".")[0]+'"']

subprocess.call(ProcessToCall, shell=True)