Check if my Python has all required packages

问题

I have a requirements.txt file with a list of packages that are required for my virtual environment. Is it possible to find out whether all the packages mentioned in the file are present. If some packages are missing, how to find out which are the missing packages?

回答1:

UPDATE:

An up-to-date and improved way to do this is via distutils.text_file.TextFile. See Acumenus' answer below for details.

ORIGINAL:

The pythonic way of doing it is via the pkg_resources API. The requirements are written in a format understood by setuptools. E.g:

Werkzeug>=0.6.1
Flask
Django>=1.3

The example code:

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)

回答2:

You can run pip freeze to see what you have installed and compare it to your requirements.txt file.

If you want to install missing modules you can run pip install -r requirements.txt and that will install any missing modules and tell you at the end which ones were missing and installed.

回答3:

Based on the answer by Zaur, assuming you indeed use a requirements file, you may want a unit test, perhaps in tests/test_requirements.py, that confirms the availability of packages.

Moreover, this approach uses a subtest to independently confirm each requirement. This is useful so that all failures are documented.

import distutils.text_file
from pathlib import Path
import unittest

import pkg_resources


REQUIREMENTS_PATH = Path(__file__).parents[1].with_name('requirements.in')


class TestRequirements(unittest.TestCase):
    def test_requirements(self):
        """Test that each requirement is available."""
        # Ref: https://stackoverflow.com/a/45474387/
        requirements = distutils.text_file.TextFile(filename=REQUIREMENTS_PATH).readlines()
        for requirement in requirements:
            with self.subTest(requirement=requirement):
                pkg_resources.require(requirement)

Note that distutils.text_file.TextFile will strip comments.

回答4:

If you're interested in doing this from the command line, pip-missing-reqs will list missing packages. Example:

$ pip-missing-reqs directory
Missing requirements:
directory/exceptions.py:11 dist=grpcio module=grpc

(pip check and pipdeptree --warn fail only audit installed packages for compatibility with each other, without checking requirements.txt.)

回答5:

You can create a virtualenv with access to the system site packages and test check whether the package (or another dependencies) are installed or not. This way the packages are not really installed (if you just want to check). An example using virtualenv wrapper would be:

$ 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...

回答6:

If requirements.txt is like :

django
oursql
sys
notexistingmodule

Then the following script will tell you which modules are missing :

#!/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)

This would print :

[ERROR] Missing module: notexistingmodule

来源：https://stackoverflow.com/questions/16294819/check-if-my-python-has-all-required-packages

标签

python

pip

requirements.txt