如何自动安装缺少的python模块？

Question

我想能够写:

try:
    import foo
except ImportError:
    install_the_module("foo")

处理此方案的推荐/惯用方法是什么？

我已经看到很多脚本只是打印错误或警告,通知用户有关丢失的模块和(有时)提供有关如何安装的说明.但是,如果我知道该模块在PyPI上可用,那么我可以更进一步地启动安装过程.没有？

Answer 1

安装问题不是源代码的主题!

您可以setup.py使用install_requires配置在包的内部正确定义依赖项.

这是要走的路......安装一些东西ImportError 是一种奇怪和可怕的结果.不要这样做.

Answer 2

try:
    import foo
except ImportError:
    sys.exit("""You need foo!
                install it from http://pypi.python.org/pypi/foo
                or run pip install foo.""")

请勿触摸用户的安装.

Answer 3

冒险负面投票,我想建议一个快速的黑客.请注意,我完全接受了应该在外部管理依赖关系的答案.

但是对于你绝对需要攻击像自包含的东西的情况,你可以尝试类似下面的东西:

import os

try:
  import requests
except ImportError:
  print "Trying to Install required module: requests\n"
  os.system('python -m pip install requests')
# -- above lines try to install requests module if not present
# -- if all went well, import required module again ( for global access)
import requests

Answer 4

这是我打电话给我的解决方案pyInstall.py.它实际上检查模块是否已安装而不是依赖ImportError(在我看来,它看起来更干净,用一个if而不是try/ 来处理它except).

我已经在版本2.6和2.7下使用了它...如果我不想print作为一个函数处理它可能会在旧版本中使用...我认为它将在版本3.0+中工作但我从来没有试了一下.

另外,正如我在我的getPip功能评论中所说,我不认为特定功能在OS X下可行.

from __future__ import print_function
from subprocess import call

def installPip(log=print):
    """
    Pip is the standard package manager for Python. Starting with Python 3.4
    it's included in the default installation, but older versions may need to
    download and install it. This code should pretty cleanly do just that.
    """
    log("Installing pip, the standard Python Package Manager, first")
    from os     import remove
    from urllib import urlretrieve
    urlretrieve("https://bootstrap.pypa.io/get-pip.py", "get-pip.py")
    call(["python", "get-pip.py"])

    # Clean up now...
    remove("get-pip.py")

def getPip(log=print):
    """
    Pip is the standard package manager for Python.
    This returns the path to the pip executable, installing it if necessary.
    """
    from os.path import isfile, join
    from sys     import prefix
    # Generate the path to where pip is or will be installed... this has been
    # tested and works on Windows, but will likely need tweaking for other OS's.
    # On OS X, I seem to have pip at /usr/local/bin/pip?
    pipPath = join(prefix, 'Scripts', 'pip.exe')

    # Check if pip is installed, and install it if it isn't.
    if not isfile(pipPath):
        installPip(log)
        if not isfile(pipPath):
            raise("Failed to find or install pip!")
    return pipPath

def installIfNeeded(moduleName, nameOnPip=None, notes="", log=print):
    """ Installs a Python library using pip, if it isn't already installed. """
    from pkgutil import iter_modules

    # Check if the module is installed
    if moduleName not in [tuple_[1] for tuple_ in iter_modules()]:
        log("Installing " + moduleName + notes + " Library for Python")
        call([getPip(log), "install", nameOnPip if nameOnPip else moduleName])

以下是一些用法示例:

from datetime  import datetime
from pyInstall import installIfNeeded

# I like to have my messages timestamped so I can get an idea of how long they take.
def log(message):
    print(datetime.now().strftime("%a %b %d %H:%M:%S") + " - " + str(message))

# The name fabric doesn't really convey to the end user why the module is needed,
# so I include a very quick note that it's used for SSH.
installIfNeeded("fabric", notes = " (ssh)", log = log)

# SoftLayer is actually named softlayer on pip.
installIfNeeded("SoftLayer", "softlayer", log = log)

编辑:获取pipPath的更多跨平台方式是:

from subprocess import Popen, PIPE
finder = Popen(['where' if isWindows() else 'which', 'pip'], stdout = PIPE, stderr = PIPE)
pipPath = finder.communicate()[0].strip()

这使得假设pip将被安装在系统路径上.它在非Windows平台上往往非常可靠,但在Windows上,最好在原始答案中使用该代码.