终端中的python3子进程pip“ImportError：无法导入名称main”

Question

我创建了一个脚本（见下文）来升级我所有的 pip 包。我通过idle3 成功执行了我的脚本，即使用idle3 打开脚本并按F5 将脚本作为模块运行。但是，我无法在终端中执行它；得到以下错误。 我该如何克服这个错误？为什么导入错误发生在终端而不是idle3？

$ python3 -m upgrade_pip_packages 
====================================================
UPGRADING ALL --USER PIP PACKAGES TO LATEST VERSION:
====================================================
Traceback (most recent call last):
  File "/usr/bin/pip", line 9, in <module>
    from pip import main
ImportError: cannot import name main
ERROR: Command 'pip list' returned non-zero exit status 1

我的脚本：upgrade_pip_packages.py

#!/bin/python3
import subprocess
from pprint import pprint


def get_pkgs():
    try:
        cmd = 'pip list'
        completed = subprocess.run( cmd, shell=True, check=True,
                                    stdout=subprocess.PIPE )
    except subprocess.CalledProcessError as err:
        print( 'ERROR:', err )
    else:
        for line in completed.stdout.decode('utf-8').splitlines()[2:]:
            yield line


def update_pkgs(piplist):
    npackages = 0
    nupgrades = 0
    nerrors = 0
    upgradelist = []
    errorlist = []
    for i in piplist:
        npackages += 1
        pkgname, ver = i.split()
        print('\n',pkgname)
        try:
            cmd = 'pip install --user {} --upgrade'.format(pkgname)
            completed = subprocess.run( cmd, shell=True, check=True,
                                        stdout=subprocess.PIPE )
        except subprocess.CalledProcessError as err:
            nerrors += 1
            errorlist.append(pkgname)
            print( 'ERROR: {}'.format(err) )
        else:
            for line in completed.stdout.decode('utf-8').splitlines():
                print(line)
                if 'Successfully installed' in line:
                    nupgrades +=1
                    upgradelist.append(pkgname)
    return npackages, nupgrades, nerrors, upgradelist, errorlist


def main():
    print('====================================================')
    print('UPGRADING ALL --USER PIP PACKAGES TO LATEST VERSION:')
    print('====================================================')
    pip_pkgs = get_pkgs() # created a generator
    npackages, nupgrades, nerrors, upgradelist, errorlist \
               = update_pkgs(pip_pkgs)
    print('\nNo. of --user pip packages = {}'.format(npackages))
    print('No. of upgrades            = {}'.format(nupgrades))
    print('No. of upgrade errors      = {}'.format(nerrors))
    if upgradelist:
        print('Package(s) upgraded:')
        pprint(upgradelist)
    if errorlist:
        print('Package(s) with upgrade error:')
        pprint(errorlist)
    print()


if __name__ == '__main__':
    main()

Answer 1

最终upgrade_pip_packages.py。

我在我的问题中找到了answer。本质上，我的脚本必须：

import sys

并进行以下修改：

cmd = [sys.executable, '-m', 'pip', 'list'] #Change here
completed = subprocess.run( cmd,
                            #shell=True, #switch this off
                            check=True,
                            stdout=subprocess.PIPE )

和

cmd = [sys.executable, '-m', 'pip', 'install', '--user', pkgname, '--upgrade'] #Change here
completed = subprocess.run( cmd,
                            #shell=True, #switch this off
                            check=True,
                            stdout=subprocess.PIPE )

PyPA documentation解释：

建议写成 {sys.executable} 而不是普通的 python 为了确保命令在 Python 安装中运行 匹配当前运行的笔记本（可能不一样 python命令引用的python安装）。

$ pip --version
pip 18.1 from ~/.local/lib/python3.5/site-packages/pip (python 3.5)
$ pip3 --version
pip 18.1 from ~/.local/lib/python3.5/site-packages/pip (python 3.5)