如果在python项目全局环境里直接使用 pip freeze > requirements.txt 会导出大量与该项目无关的依赖，包括很多个包信息，其实这里是把你当前 python 环境的所有包的相关信息导出来了。如果我们只需导出当前项目所需的依赖包，还可以采用另外一种方式，使用工具：pipreqs
1、安装pipreqs：
pip install pipreqs
官方网站
2、进入当前项目目录下，导出依赖清单：
pipreqs ./
导包完成会在项目路径下生成一个requirements.txt文件。
如果遇到编码错误UnicodeDecodeError，则将指定编码为utf8：
pipreqs ./ --encoding=utf8
pipreqs ./ --encoding='iso-8859-1'
Usage:
Usage:
pipreqs [options] [<path>]
Arguments:
<path> The path to the directory containing the application files for which a requirements file
should be generated (defaults to the current working directory)
Options:
--use-local Use ONLY local package info instead of querying PyPI
--pypi-server <url> Use custom PyPi server
--proxy <url> Use Proxy, parameter will be passed to requests library. You can also just set the
environments parameter in your terminal:
$ export HTTP_PROXY="http://10.10.1.10:3128"
$ export HTTPS_PROXY="https://10.10.1.10:1080"
--debug Print debug information
--ignore <dirs>... Ignore extra directories, each separated by a comma
--no-follow-links Do not follow symbolic links in the project
--encoding <charset> Use encoding parameter for file open
--savepath <file> Save the list of requirements in the given file
--print Output the list of requirements in the standard output
--force Overwrite existing requirements.txt
--diff <file> Compare modules in requirements.txt to project imports
--clean <file> Clean up requirements.txt by removing modules that are not imported in project
--mode <scheme> Enables dynamic versioning with <compat>, <gt> or <non-pin> schemes
<compat> | e.g. Flask~=1.1.2
<gt> | e.g. Flask>=1.1.2
<no-pin> | e.g. Flask
