How to co-exist multiple versions of Python on Windows

1, if it is windows, it is recommended to change the PIP under the installation path to PIP2 and PIP3 respectively.
2, if it is Linux, is the same way, will be the soft link pip deleted, add pip2 and PIP3 software to differentiate. PIP will automatically install the corresponding package

At present, the domestic website will often let everyone change one of the Python.exe name (well, I also said, here to correct it), so that the name of the two executable file, but there is a major hidden danger, is that the name of the Python to modify the corresponding PIP will not be used.

What is the official solution?

In fact, the problem was that the Python community gave the official solution a few years ago, but it has not been noticed at home.

When we installed Python3 (>=3.3), the Python installation package actually installed a launcher Py.exe in the system, which was placed by default under Folder C:\Windows\. This initiator allows us to specify whether to run the code using PYTHON2 or Python3 (if you have successfully installed Python2 and Python3).

For installation of Python2 and 3, see Python Tribe (http/python.freelycode.com)--Video Academy--0 Basics 1 hours, getting started with Python The first section.

If you have a python file called hello.py, then you can run it with Python2 like this

Py-2 hello.py

Similarly, if you want to run it with Python3, that's it.

Py-3 hello.py

Remove Parameter -2/-3

Adding parameter -2/-3 to each run is still a hassle, so py.exe this launcher allows you to add a description to the code to indicate whether the file should be run by python2 or interpreted by Python3. The way to do this is to add a line at the beginning of the code file

#! Python2

Or

#! Python3

Indicates that the code file is run with Python2 or Python3 interpretation, respectively. This way, your commands can be simplified when you run them to

PY hello.py

Using PIP

When Python2 and Python3 are present on Windows, their corresponding Pip is called Pip.exe, so it is not possible to install the package directly using the PIP Install command. Instead, you use the initiator Py.exe to specify the version of the PIP. The command is as follows:

Py-2-m pip install XXXX

2 still means to run the PIP module using python2,-m pip, that is to run the PIP command. If the software is installed for Python3, then the command resembles

Py-3-m pip install XXXX

#! Python2 and # Coding:utf-8 which one is written in front?

There is another confusion for Python2 users, Python2 to add a line of instructions at the top of the code file to be able to use Chinese in the code. If you indicate that the Python version you are using also needs to add a line to the top of the file, which line should be on the first row?

#! The python2 needs to be placed on the first line, and the coding instructions can be placed on the second line. So the beginning of the file should resemble:

#! python2# Coding:utf-8

With these tips, Python2 and Python3 can happily play together.

Python standard: PEP 397--python launcher for Windows