Python Virtual Environment

Virtual environmnet workflow

# Install virtualenv module
$ pip install --user virtualenv

# Create a new virtual env
$ py -m venv env

# Activate the new virtual env
$ .\env\Scripts\activate

# Install all the required packages from requirements.txt
$ pip install -r requirements.txt

# De-activate the new virtual env
$ deactivate

Using virtualenvwrapper

It’s advantage is that it keeps all virtual env in one place (~/.virtualenvs)
pip install --user virtualenvwrapper

Add these lines in .bashrc

export VIRTUALENVWRAPPER_PYTHON="/usr/bin/python3"
source ~/.local/bin/virtualenvwrapper.sh

source ~/.bashrc

Create a virtual environments

$ mkvirtualenv --python=python3.6 virt-env-name

List virtual envs.
```
$ lsvirtualenv
```
Enter virtual environments
```
$ workon virtual-env-name
```
Exit virtual env
```
$ deactivate
```
Delete/remove a virtual environment
```
$ rmvirtualenv ENVNAME
```

Virtualenvwrapper (From test driven develoment book)

Install virtualenvwrapper
```
$ pip install --user virtualenvwrapper
```

Put these lines in .bashrc

export VIRTUALENVWRAPPER_PYTHON="/usr/bin/python3"
source ~/.local/bin/virtualenvwrapper.sh

Create virtual environment

$ mkvirtualenv --python=python3.6 virt_env_sname

Conda and virtual environments

Create a virtual environment

$ conda create --name $ENVIRONMENT_NAME python

Activate an environment
```
$ source activate $ENVIRONMENT_NAME
```
Deactivate an environment
```
$ source deactivate
```
Create requirements file
```
$ conda list --export
```
List all environments
```
$ conda info --envs
```

Python virtual environments using pyenv

Install your preferred Python version (to be run only once)
```
$ pyenv install 3.6.5
```
Make it a virtualenv so you can make others later if you want
```
$ pyenv virtualenv 3.6.5 myenv
```
Make it globally active (for your user)
```
$ pyenv global myenv
```
Delete the virtualenv
```
$ pyenv uninstall myenv
```
Make a new one
```
$ pyenv virtualenv 3.6.5 myenv
```
Make environments active per-directory
```
$ pyenv local myenv
```

will drop a .python-version file into your current folder and any time you invoke Python or pip-installed Python utilities from it or under it, they will be shimmed by pyenv.

Source : https://askubuntu.com/questions/865554/how-do-i-install-python-3-6-using-apt-get/865644#865644

Create a virtual environment for a specific Python version.
```
$ pyenv virtualenv 3.4.3 my_env_3_4
```

Create a virtual environment based on the current Python version.

$ pyenv version
2.7.10 (set by /Users/akbar/.pyenv/version)
$ pyenv virtualenv my_env_2_7

This will create a virtual environment based on Python 2.7.10 under the pyenv root in a directory called my_env_2_7.

List existing virtual environments created by pyenv.
```
$ pyenv virtualenvs
```
The pyenv versions command will also show the virtual environments along with the installed versions of Python.
```
$ pyenv versions
```
If eval "$(pyenv virtualenv-init -)" is configured in your shell, pyenv-virtualenv will automatically activate/deactivate virtualenvs on entering/leaving directories which contain a .python-version file that contains the name of a valid virtual environment as shown in the output of pyenv virtualenvs. For manual activation/deactivation, see 5 and 6.
To manually activate a virtual environment.
```
$ pyenv activate my_env_2_7
```
To manually deactivate a virtual environment.
```
(my_env_2_7)$ pyenv deactivate
```
Delete a virtual environment.
```
$ pyenv uninstall my_env_2_7
```

Source : http://akbaribrahim.com/managing-python-virtual-environments-with-pyenv-virtualenv/