Python 中的包或模块具有依赖关系。有时候离线安装时总会提示缺少依赖包，此时就需要知道安装的模块依赖哪些包。然后下载相应的模块即可。那如何查看某个模块的依赖包有哪些呢？本篇介绍一些方法。

使用 pip

如果模块是通过 pip 安装的，而不是通过 conda 安装的，可以使用如下的方法查看

pip show visdom

结果大概是这样

Name: visdom
Version: 0.1.8.9
Summary: A tool for visualizing live, rich data for Torch and Numpy
Home-page: https://github.com/facebookresearch/visdom
Author: Jack Urbanek, Allan Jabri, Laurens van der Maaten
Author-email: [email protected]
License: CC-BY-NC-4.0
Location: /usr/local/miniconda/lib/python3.9/site-packages
Requires: pyzmq, scipy, requests, tornado, six, torchfile, jsonpatch, websocket-client, pillow, numpy
Required-by:

从上面可以清楚的看到模块 visdom 的依赖模块有 pyzmq, scipy, requests, tornado, six, torchfile, jsonpatch, websocket-client, pillow, numpy

使用 pipdeptree

直接使用 pip 查看能够简单的看到依赖包，使用 pipdeptree 模块能够方便的查看更详细的依赖关系。不过，在这之前，需要先安装该模块

pip install pipdeptree

查看 visdom 的依赖关系

pipdeptree -p visdom

结果大概如下

visdom==0.1.8.9
  - jsonpatch [required: Any, installed: 1.32]
    - jsonpointer [required: >=1.9, installed: 2.3]
  - numpy [required: >=1.8, installed: 1.22.4]
  - pillow [required: Any, installed: 9.1.1]
  - pyzmq [required: Any, installed: 23.2.0]
  - requests [required: Any, installed: 2.27.1]
    - certifi [required: >=2017.4.17, installed: 2022.6.15]
    - charset-normalizer [required: ~=2.0.0, installed: 2.0.4]
    - idna [required: >=2.5,<4, installed: 3.3]
    - urllib3 [required: >=1.21.1,<1.27, installed: 1.26.9]
  - scipy [required: Any, installed: 1.8.1]
    - numpy [required: >=1.17.3,<1.25.0, installed: 1.22.4]
  - six [required: Any, installed: 1.16.0]
  - torchfile [required: Any, installed: 0.1.0]
  - tornado [required: Any, installed: 6.1]
  - websocket-client [required: Any, installed: 1.3.3]

从上面的结果可以看出，依赖关系更加详细，不仅能查看一级依赖还能查看二级依赖，同时，能够看到依赖的包的版本要求。

更多关于 pipdeptree 的使用，可以使用如下方法查看

pipdeptree -h

usage: pipdeptree [-h] [-v] [-f] [--python PYTHON] [-a] [-l] [-u] [-w [{silence,suppress,fail}]] [-r] [-p PACKAGES] [-e PACKAGES] [-j]
                  [--json-tree] [--graph-output OUTPUT_FORMAT]

Dependency tree of the installed python packages

optional arguments:
  -h, --help            show this help message and exit
  -v, --version         show program's version number and exit
  -f, --freeze          Print names so as to write freeze files
  --python PYTHON       Python to use to look for packages in it (default: where installed)
  -a, --all             list all deps at top level
  -l, --local-only      If in a virtualenv that has global access do not show globally installed packages
  -u, --user-only       Only show installations in the user site dir
  -w [{silence,suppress,fail}], --warn [{silence,suppress,fail}]
                        Warning control. "suppress" will show warnings but return 0 whether or not they are present. "silence" will not
                        show warnings at all and always return 0. "fail" will show warnings and return 1 if any are present. The
                        default is "suppress".
  -r, --reverse         Shows the dependency tree in the reverse fashion ie. the sub-dependencies are listed with the list of packages
                        that need them under them.
  -p PACKAGES, --packages PACKAGES
                        Comma separated list of select packages to show in the output. If set, --all will be ignored.
  -e PACKAGES, --exclude PACKAGES
                        Comma separated list of select packages to exclude from the output. If set, --all will be ignored.
  -j, --json            Display dependency tree as json. This will yield "raw" output that may be used by external tools. This option
                        overrides all other options.
  --json-tree           Display dependency tree as json which is nested the same way as the plain text output printed by default. This
                        option overrides all other options (except --json).
  --graph-output OUTPUT_FORMAT
                        Print a dependency graph in the specified output format. Available are all formats supported by GraphViz, e.g.:
                        dot, jpeg, pdf, png, svg