python - 如何在运行时安装和导入 Python 模块？

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 安装成功，但是下一行import pexpect 失败。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

另一个镜头:

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]

您应该考虑使用 requirements.txt连同点子。好像您正在尝试自动化部署(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#