平常在项目开发中，我们可以很容易的通过pip install packname安装python第三方包，但在项目上线前，我们该如何将该项目所需要的第三方包及其依赖包放到python虚拟开发环境中呢？
例如：我在环境中装了python的celery库，现在我想把celery包及其安装所依赖的包导出来，以便可以放在另一台机器上（无外网访问权限）的python虚拟环境直接使用
方法1只列出了celery包的主依赖包pytz, billiard, kombu, vine，
方法2列出了celery包的主依赖包与各主依赖包所依赖的包，但看起来比较乱
方法3以树结构形式列出了celery包的主依赖包与各主依赖包的子依赖包，可读性好，一目了然，建议使用此法。
方法1：
(poc)[root@zq ~]# pip show celery
Name: celery
Version: 4.3.0
Location: /opt/poc/lib/python2.7/site-packages/celery-4.3.0-py2.7.egg
Requires: pytz, billiard, kombu, vine: #主依赖项，这些主依赖项还依赖于其它包方法2：
(poc)[root@zq ~]# pip install celery
Requirement already satisfied (use --upgrade to upgrade): celery in /opt/poc/lib/python2.7/site-packages/celery-4.3.0-py2.7.egg
Requirement already satisfied (use --upgrade to upgrade): pytz>dev in /opt/poc/lib/python2.7/site-packages (from celery)
Requirement already satisfied (use --upgrade to upgrade): billiard<4.0,>=3.6.0 in /opt/poc/lib/python2.7/site-packages/billiard-3.6.1.0-py2.7.egg (from celery)
Requirement already satisfied (use --upgrade to upgrade): kombu<5.0,>=4.4.0 in /opt/poc/lib/python2.7/site-packages/kombu-4.6.6-py2.7.egg (from celery)
Requirement already satisfied (use --upgrade to upgrade): vine>=1.3.0 in /opt/poc/lib/python2.7/site-packages (from celery)
Requirement already satisfied (use --upgrade to upgrade): amqp<2.6,>=2.5.2 in /opt/poc/lib/python2.7/site-packages/amqp-2.5.2-py2.7.egg (from kombu<5.0,>=4.4.0->celery)
Requirement already satisfied (use --upgrade to upgrade): importlib-metadata>=0.18 in /opt/poc/lib/python2.7/site-packages/importlib_metadata-0.23-py2.7.egg (from kombu<5.0,>=4.4.0->celery)
Requirement already satisfied (use --upgrade to upgrade): configparser>=3.5 in /opt/poc/lib/python2.7/site-packages/configparser-4.0.2-py2.7.egg (from importlib-metadata>=0.18->kombu<5.0,>=4.4.0->celery)
Requirement already satisfied (use --upgrade to upgrade): contextlib2 in /opt/poc/lib/python2.7/site-packages/contextlib2-0.6.0.post1-py2.7.egg (from importlib-metadata>=0.18->kombu<5.0,>=4.4.0->celery)
Requirement already satisfied (use --upgrade to upgrade): pathlib2 in /opt/poc/lib/python2.7/site-packages/pathlib2-2.3.5-py2.7.egg (from importlib-metadata>=0.18->kombu<5.0,>=4.4.0->celery)
Requirement already satisfied (use --upgrade to upgrade): zipp>=0.5 in /opt/poc/lib/python2.7/site-packages/zipp-0.6.0-py2.7.egg (from importlib-metadata>=0.18->kombu<5.0,>=4.4.0->celery)
Requirement already satisfied (use --upgrade to upgrade): scandir in /opt/poc/lib/python2.7/site-packages (from pathlib2->importlib-metadata>=0.18->kombu<5.0,>=4.4.0->celery)
Requirement already satisfied (use --upgrade to upgrade): six in /opt/poc/lib/python2.7/site-packages (from pathlib2->importlib-metadata>=0.18->kombu<5.0,>=4.4.0->celery)
Requirement already satisfied (use --upgrade to upgrade): more-itertools in /opt/poc/lib/python2.7/site-packages (from zipp>=0.5->importlib-metadata>=0.18->kombu<5.0,>=4.4.0->celery)
Cleaning up...
方法3：与方法2的结果一致
推荐使用方法3
(poc)[root@zhangqiang ~]# pipdeptree -p celery #能显示所有的依赖包及其子包
Warning!!! Possibly conflicting dependencies found:
* arrow==0.15.4
- backports.functools-lru-cache [required: >=1.2.1, installed: ?]
* cryptography==2.4.2
- idna [required: >=2.1, installed: ?]
* cffi==1.12.3
- pycparser [required: Any, installed: ?]
------------------------------------------------------------------------
celery==4.3.0
- billiard [required: >=3.6.0,<4.0, installed: 3.6.1.0]
- kombu [required: >=4.4.0,<5.0, installed: 4.6.6]
- amqp [required: >=2.5.2,<2.6, installed: 2.5.2] #kombu的依赖项
- vine [required: >=1.1.3,<5.0.0a1, installed: 1.3.0]
- importlib-metadata [required: >=0.18, installed: 0.23]
- configparser [required: >=3.5, installed: 4.0.2]
- contextlib2 [required: Any, installed: 0.6.0.post1]
- pathlib2 [required: Any, installed: 2.3.5]
- scandir [required: Any, installed: 1.10.0]
- six [required: Any, installed: 1.10.0]
- zipp [required: >=0.5, installed: 0.6.0]
- more-itertools [required: Any, installed: 4.2.0]
- six [required: >=1.0.0,<2.0.0, installed: 1.10.0]
- pytz [required: >dev, installed: 2017.2]
- vine [required: >=1.3.0, installed: 1.3.0]
