Setting python working environment on window

04 Jun 2017 python window python2x-3x

Download and install python 2x, 3x

Download both python 2x, 3x from python download page
The installation steps on window are easy, just click next then next…. please notice the installation path
Adding installed python scripts directory into System path. This folder contains command files for certain pakages (ex: pip, virtualenv)
1. Go to start menu > right click on computer > properties > advanced system settings > Environment variables
2. Create new variables: PYTHON2_SCRIPTS (C:\Python27\Scripts), PYTHON3_SCRIPTS (C:\Python36-32\Scripts)
3. Add newly created varibale into Path: append to the end %PYTHON2_SCRIPTS%;%PYTHON3_SCRIPTS%

Working with mutiple version of python on window

After above steps we have both python 2x, python 3x installed in system.

How to specify which python version to run from cmd?

Use python launcher. From python 3x, python has a launcher called py.exe which you can specify python version to run (ex: py -2, py -3)

usage: py [ launcher-arguments ] [ python-arguments ] script [ script-arguments ]
py -h for more information

How to specify which pip version to run?

python already have separate pip version for each as in picture above. one more step that I did is change the pip from both to pip-bak to not wrongly use it without specify version. you can keep pip from which version if you want it will be the default.

How to use pip

Usage:
	pip <command [options]
pip -h for more help

Some common usage

get help for specific pip command
```
pip help install 
```
search for package
```
pip search virtualenv 
```

install package

pip install virtualenv
pip install virtualenv==x.y # install specific version of package

uninstall package
```
pip uninstall virtualenv
```
show information about package
```
pip show virtualenv
```
install multiple package from a requirements.txt file
```
pip install -r requirements.txt
```

create requirements.txt file

pip freeze > requirements.txt
pip freeze --local > requirements.txt # if in virtualenv

uninstall multiple package from a file (requirements.txt)
```
pip uninstall -r requirements.txt
```

list installed package

pip list
pip list -o # list outdated package

upgrade outdated package to latest
```
pip install -U virtualenv
```

Install virtualenv package and setting a python virtual environment

For why we should use virtualenv you can check here: Virtual Environments. The main idea is to have isolate working environment for each of your python project.

Because of functional are the same, you can install virtualenv for either python 2.x or 3.x (3.x for me). You can install it using pip as below:

pip3 install virtualenv

Now you can use virtualenv to create a working environment for your project

for python 3.x project: virtualenv -p C:\Python36-32\python.exe venv36
for python 2.x project: virtualenv -p C:\Python27\python.exe venv27

Using newly created environment:

venv27\Scripts\activate to start working
python -V to check python version
deactivate to stop working

MEMTO