python rely on database management and migration

Why

python package particularly large, this is handy for us also caused unchanged, the main questions are as follows:

1. When developing environmental transport, we want all of the existing installation packages to install it again on the new machine;
2. Changes in the larger package has been installed in the subsequent updates that may affect existing code. Hope can be performed in a different environment.

What

There are currently three python dependencies management:

1. Conda , I believe we no stranger to anaconda;
2. PIP , management of third-party libraries;
3. Docker , containerization is now a program very fire. docker container collapse will not affect the host, and portability is very strong environmental image can be easily transplanted to up to a different host environment without the need to reconfigure the installation. (First dig a hole here, after the new East etc. God to teach again supplement)
4. virtualenv is a tool to build custom virtual environment for python, python versions can be specified in a virtual environment and use pip install to activate the virtual environment;

How

Use conda and problems

Pack away his own environment, to note that conda need exactly the same environment.
For example, I built a virtual environment python2.7 in the local, the address in

/Users/shang/anaconda3/envs/py27

You can look at bin/pipwhat is in the file

#!/Users/shang/anaconda3/envs/py27/bin/python

# -*- coding: utf-8 -*-
import re
import sys

from pip._internal import main

if __name__ == '__main__':
    sys.argv[0] = re.sub(r'(-script\.pyw?|\.exe)?$', '', sys.argv[0])
    sys.exit(main())

Notes that the first line, is designated pythonpath, but also the absolute path , if done environments migrating between servers, should be able to do the same to ensure the path, such as are

/home/work/software/anaconda3/envs/py27/bin/python

Use pip

This method is relatively simple table use is to first know what the package was originally installed, and then install it again in a new environment. This is good, better than run again .pygood document to report a wrong way to install a package ==

pip freeze > requirements.txt  #获得依赖包
pip install -r requirements.txt #安装依赖包

Note: pip freeze output is that all three parties packet information in the local environment, but will be less than a few packages pip list, because the pip, wheel, setuptools package, etc., are built-in and can not be (un) install, if you want to display all package can add parameters -all, i.e. pip freeze -all

Use docker

to be continued