如何在运行时安装和导入Python模块？圣保罗

Question

我想编写一个脚本来自动设置一个全新的ubuntu安装并安装一个基于django的应用程序。由于脚本将在新服务器上运行，因此Python脚本需要自动安装一些必需的模块。

这是脚本。

#!/usr/bin/env python

import subprocess
import os
import sys

def pip_install(mod):
    print subprocess.check_output("pip install %s" % mod, shell=True)

if __name__ == "__main__":
    if os.getuid() != 0:
        print "Sorry, you need to run the script as root."
        sys.exit()

    try:
        import pexpect
    except:
        pip_install('pexpect') 
        import pexpect        

    # More code here...

pexpect的安装是成功的，但下一行import pexpect失败了。我认为这是因为在运行时代码不知道新安装的pexpect。

如何在运行时安装和导入Python模块？我对其他方法持开放态度。

Answer 1

您可以导入pip而不是使用子进程：

import pip

def install(package):
    pip.main(['install', package])

# Example
if __name__ == '__main__':
    try:
        import pexpect
    except ImportError:
        install('pexpect')
        import pexpect

另一个需要：

import pip

def import_with_auto_install(package):
    try:
        return __import__(package)
    except ImportError:
        pip.main(['install', package])
    return __import__(package)

# Example
if __name__ == '__main__':
    pexpect = import_with_auto_install('pexpect')
    print(pexpect)

[编辑]

你应该考虑使用requirements.txt和pip。好像你正试图自动化部署（这很好！），在我的工具带中我还有virtualenvwrapper，vagrant和ansible。

这是我的输出：

(test)root@vagrant:~/test# pip uninstall pexpect
Uninstalling pexpect:
  /usr/lib/python-environments/test/lib/python2.6/site-packages/ANSI.py
  /usr/lib/python-environments/test/lib/python2.6/site-packages/ANSI.pyc
  /usr/lib/python-environments/test/lib/python2.6/site-packages/FSM.py
  /usr/lib/python-environments/test/lib/python2.6/site-packages/FSM.pyc
  /usr/lib/python-environments/test/lib/python2.6/site-packages/fdpexpect.py
  /usr/lib/python-environments/test/lib/python2.6/site-packages/fdpexpect.pyc
  /usr/lib/python-environments/test/lib/python2.6/site-packages/pexpect-2.4-py2.6.egg-info
  /usr/lib/python-environments/test/lib/python2.6/site-packages/pexpect.py
  /usr/lib/python-environments/test/lib/python2.6/site-packages/pexpect.pyc
  /usr/lib/python-environments/test/lib/python2.6/site-packages/pxssh.py
  /usr/lib/python-environments/test/lib/python2.6/site-packages/pxssh.pyc
  /usr/lib/python-environments/test/lib/python2.6/site-packages/screen.py
  /usr/lib/python-environments/test/lib/python2.6/site-packages/screen.pyc
Proceed (y/n)? y
  Successfully uninstalled pexpect
(test)root@vagrant:~/test# python test.py
Downloading/unpacking pexpect
  Downloading pexpect-2.4.tar.gz (113Kb): 113Kb downloaded
  Running setup.py egg_info for package pexpect
Installing collected packages: pexpect
  Running setup.py install for pexpect
Successfully installed pexpect
Cleaning up...
<module 'pexpect' from '/usr/lib/python-environments/test/lib/python2.6/site-packages/pexpect.pyc'>
(test)root@vagrant:~/test#

Answer 2

我使用imp模块解决了我的问题。

#!/usr/bin/env python

import pip
import imp

def install_and_load(package):
    pip.main(['install', package])

    path = '/usr/local/lib/python2.7/dist-packages'
    if path not in sys.path:
        sys.path.append(path)

    f, fname, desc = imp.find_module(package)
    return imp.load(package, f, fname, desc)

if __name__ == "__main__":
    try:
        import pexpect
    except:
        pexpect = install_and_load('pexpect')

    # More code...

实际上代码不太理想，因为我需要对Python模块目录进行硬编码。但由于该脚本适用于已知的目标系统，我认为这是可以的。

Answer 3

我实际上为这个目的制作了一个模块（impstall）

它真的很容易使用：

import impstall
impstall.now('pexpect')
impstall.now('wx', pipName='wxPython')

Github link for issues/contributions

Answer 4

对于那些使用大于10.x的pip版本的人来说，main没有pip函数，所以替代方法是使用import pip._internal as pip而不是import pip，如：

Updated answer of Paulo

import pip._internal as pip

def install(package):
    pip.main(['install', package])

if __name__ == '__main__':
    try:
        import pexpect
    except ImportError:
        install('pexpect')
        import pexpect