python - 为什么 pip 会卸载所需的包？

Question

pip似乎大肆卸载需要的包!如果某个包显式声明了某个包的特定版本，则 pip 似乎应该无法卸载该包，但事实并非如此。考虑:

$ pip list | grep bar
bar           1.0    
$ cat setup.py 

from setuptools import setup, find_packages

def do_setup():
    setup(
        name='foo',
        description='the foo package',
        license='MIT',
        version='1.0',
        install_requires=[
            'bar==1.0',
        ],
    )

if __name__ == "__main__":
    do_setup()
$ pip install .
Processing /Users/williamp/examples/pip/foo
  Requirement already satisfied (use --upgrade to upgrade): foo==1.0 from file:///Users/williamp/examples/pip/foo in /Users/williamp/tmp/virt/lib/python2.7/site-packages
Requirement already satisfied: bar==1.0 in /Users/williamp/tmp/virt/lib/python2.7/site-packages (from foo==1.0)
$ cd ../bar
$ pip install dist/bar-1.1.tar.gz 
Processing ./dist/bar-1.1.tar.gz
Building wheels for collected packages: bar
  Running setup.py bdist_wheel for bar ... done
  Stored in directory: /Users/williamp/Library/Caches/pip/wheels/bf/d3/68/6016190bb2084f62ba1107c63bea948f4cfbb2c129fa0cb102
Successfully built bar
Installing collected packages: bar
  Found existing installation: bar 1.0
    Uninstalling bar-1.0:
      Successfully uninstalled bar-1.0
Successfully installed bar-1.1

似乎我最终遇到了这样的情况:安装了软件包 foo 并明确依赖于 bar == 1.0，但 pip 已卸载 bar 1.0 并且系统现在处于不稳定状态。是否有一些简单的配置选项可以传递给 pip 来告诉它不要这样做？

Answer 1

否，但您可以通过运行 pip check 手动检查:

$ pip check
No broken requirements found.
$ pip uninstall pytz
Uninstalling pytz-2017.3:
  ...
Proceed (y/n)? y
  Successfully uninstalled pytz-2017.3
$ pip check
Django 2.0 requires pytz, which is not installed.

依赖关系跟踪已 a major issue现在用 pip 一段时间了。我希望它最终会得到修复。