如何自动安装缺少的 python 模块？

Question

我希望能够写：

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

处理这种情况的推荐/惯用方法是什么？

我见过很多脚本只是打印错误或警告，通知用户缺少模块，并（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，那么我肯定可以更进一步安装过程。不？

Answer 1

冒着投反对票的风险，我想建议一个快速破解方法。请注意，我完全同意接受的答案：依赖关系应该在外部进行管理。

但对于您绝对需要破解类似自包含的东西的情况，您可以尝试如下所示：

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 2

安装问题不是源代码的主题！

您可以在包的 setup.py 中正确定义依赖项
使用 install_requires 配置。

这就是要走的路......由于 ImportError 安装某些东西
有点奇怪和可怕。不要这样做。

Answer 3

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

不要碰用户的安装。

Answer 4

这是我整理的解决方案，我将其称为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，使用 if 而不是 try 来处理此问题看起来更干净/除外）。

我在版本 2.6 和 2.7 下使用过它...如果我不想将 print 作为函数处理...它可能会在旧版本中工作...并且我认为它会在旧版本中工作3.0+版本，但我从未尝试过。

另外，正如我在 getPip 函数的注释中指出的那样，我认为该特定函数无法在 OS X 下工作。

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])

以下是一些使用示例：

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：A获取 pipPath 的更多跨平台方法是：

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

这假设 pip 已/将安装在系统路径上。它在非 Windows 平台上往往相当可靠，但在 Windows 上，最好使用我原来答案中的代码。