如何检查我的Python是否具有所有必需的包？

Question

我有一个requirements.txt文件，其中包含我的虚拟环境所需的软件包列表。是否有可能找出文件中提到的所有软件包是否都存在。如果缺少一些软件包，如何找出哪些是缺失的软件包？

Answer 1

的Python的这样做的方式是通过pkg_resourcesAPI。这些需求以setuptools可理解的格式编写。 E.g：

Werkzeug>=0.6.1 
Flask 
Django>=1.3 

的示例代码：

import pkg_resources 
from pkg_resources import DistributionNotFound, VersionConflict 

# dependencies can be any iterable with strings, 
# e.g. file line-by-line iterator 
dependencies = [ 
    'Werkzeug>=0.6.1', 
    'Flask>=0.9', 
] 

# here, if a dependency is not met, a DistributionNotFound or VersionConflict 
# exception is thrown. 
pkg_resources.require(dependencies) 

Answer 2

您可以运行pip freeze以查看您已安装的内容并将其与您的requirements.txt文件进行比较。

如果你想安装缺少的模块，你可以运行pip install -r requirements.txt，那将安装任何缺少的模块，并告诉你最后哪些缺失和安装。

Answer 3

如果requirements.txt是这样的：

django 
oursql 
sys 
notexistingmodule 

然后将下面的脚本会告诉你哪些模块丢失：

#!/usr/bin/python3 
fname = 'requirements.txt' 
with open(fname, 'r', encoding='utf-8') as fhd: 
    for line in fhd: 
     try: 
      exec("import " + line) 
     except: 
      print("[ERROR] Missing module:", line) 

这将打印：

[ERROR] Missing module: notexistingmodule 

Answer 4

您可以创建一个与virtualenv中访问系统的网站打包并测试检查包装（或其他依赖关系）是否安装与否。这种方式包没有真正安装（如果你只是想检查）。使用virtualenv wrapper一个例子是：

$ cat requirements.txt 
requests 
simplejson 

$ mkvirtualenv --system-site-packages test 
Running virtualenv with interpreter /usr/bin/python2 
New python executable in test/bin/python2 
Also creating executable in test/bin/python 
Installing setuptools, pip...done. 

$ pip install -r requirements.txt 
Downloading/unpacking requests (from -r requirements.txt (line 1)) 
    Downloading requests-2.10.0-py2.py3-none-any.whl (506kB): 506kB downloaded 
Requirement already satisfied (use --upgrade to upgrade): simplejson in /usr/lib/python2.7/dist-packages (from -r requirements.txt (line 2)) 
Installing collected packages: requests 
Successfully installed requests 
Cleaning up... 

$ pip install -r requirements.txt 
Requirement already satisfied (use --upgrade to upgrade): requests in /home/yucer/.virtualenvs/test/lib/python2.7/site-packages (from -r requirements.txt (line 1)) 
Requirement already satisfied (use --upgrade to upgrade): simplejson in /usr/lib/python2.7/dist-packages (from -r requirements.txt (line 2)) 
Cleaning up... 

$ deactivate 

$ rmvirtualenv test 
Removing test... 

Answer 5

基础上answer by Zaur，假设你确实使用requirements.txt文件，您可以在tests/test_requirements.py需要一个单元测试，也许，确认包的可用性。

的一般方法是：

import pathlib 
import unittest 

import pip 
import pkg_resources 


class TestRequirements(unittest.TestCase): 

    def test_requirements(self): # pylint: disable=no-self-use 
     """Recursively confirm that requirements are available. 

     This implementation is tested to be compatible with pip 9.0.1. 
     """ 
     requirements_path = pathlib.Path(__file__).parents[1]/'requirements.txt' 
     requirements = pip.req.parse_requirements(str(requirements_path), session=pip.download.PipSession()) 
     requirements = [str(r.req) for r in requirements] 
     pkg_resources.require(requirements) 

注意，这个答案使用pathlib它可在Python 3而不是在Python 2.如果使用Python 2，先安装它的反向移植是pathlib2。