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How to create virtual environments for different applications?
Just imagine that you have an application which is fully developed and you do not want to make any changes to the libraries it is using but at the same time you start developing another application which requires the updated versions of those libraries. What will you do ? It is where virtual environments come into play…
A Virtual Environment, put simply, is an isolated working copy of Python which allows you to work on a specific project without worry of affecting other projects. It enables multiple side-by-side installations of Python, one for each project. It doesn’t actually install separate copies of Python, but it does provide a clever way to keep different project environments isolated because it isolates environmental variables and packages. It is the cure to error messages that complain about the wrong python package version.
Here are some popular libraries/tools for you to create virtual environment in Python: virtualenv, virtualenvwrapper, pvenv and venv. Here, we are going to focus on virtualenv package.
It is highly likely that that virtualenv is already installed on your system. However, check if you have it or which version you are using:
which virtualenv
or
virtualenv --version
If not, you need to install the package virtualenv package:
(base) Arat-MacBook-Pro:~ mustafamuratarat$ pip3 install virtualenv
Collecting virtualenv
Downloading virtualenv-20.0.20-py2.py3-none-any.whl (4.7 MB)
|████████████████████████████████| 4.7 MB 262 kB/s
Collecting distlib<1,>=0.3.0
Downloading distlib-0.3.0.zip (571 kB)
|████████████████████████████████| 571 kB 363 kB/s
Collecting appdirs<2,>=1.4.3
Downloading appdirs-1.4.3-py2.py3-none-any.whl (12 kB)
Requirement already satisfied: six<2,>=1.9.0 in /Users/mustafamuratarat/anaconda3/lib/python3.7/site-packages (from virtualenv) (1.12.0)
Requirement already satisfied: importlib-metadata<2,>=0.12; python_version < "3.8" in /Users/mustafamuratarat/anaconda3/lib/python3.7/site-packages (from virtualenv) (1.6.0)
Requirement already satisfied: filelock<4,>=3.0.0 in /Users/mustafamuratarat/anaconda3/lib/python3.7/site-packages (from virtualenv) (3.0.12)
Requirement already satisfied: zipp>=0.5 in /Users/mustafamuratarat/anaconda3/lib/python3.7/site-packages (from importlib-metadata<2,>=0.12; python_version < "3.8"->virtualenv) (0.5.1)
Building wheels for collected packages: distlib
Building wheel for distlib (setup.py) ... done
Created wheel for distlib: filename=distlib-0.3.0-py3-none-any.whl size=340428 sha256=fc418a7494feb2b03cf1be1b75fc5ba1edca92d03922c1ef275af55d309e0506
Stored in directory: /Users/mustafamuratarat/Library/Caches/pip/wheels/a2/19/da/a15d4e2bedf3062c739b190d5cb5b7b2ecfbccb6b0d93c861b
Successfully built distlib
Installing collected packages: distlib, appdirs, virtualenv
Successfully installed appdirs-1.4.3 distlib-0.3.0 virtualenv-20.0.20
Once that is done, go to the folder where your application will reside in and do what’s given below, which will call the program virtualenv we installed, and it is going to create a folder called venv inside our current folder and in venv it is going put a fresh Python 3.7.3 installation (you can of course change the Python version you want to install).
(base) Arat-MacBook-Pro:REST APIs with Flask and Python mustafamuratarat$ virtualenv venv --python=python3.7.3
The command above creates a venv/ directory in your project where all dependencies are installed. You need to activate your isolated environment first though (in every terminal instance where you are working on your project):
(base) Arat-MacBook-Pro:REST APIs with Flask and Python mustafamuratarat$ source venv/bin/activate
(venv) (base) Arat-MacBook-Pro:REST APIs with Flask and Python mustafamuratarat$
This will fire up a shell (as you see the shell is now on venv not base) for your environment.
Now you can install any packages you want in this environment:
(venv) (base) Arat-MacBook-Pro:REST APIs with Flask and Python mustafamuratarat$ pip3 install Flask-RESTful
Collecting Flask-RESTful
Downloading Flask_RESTful-0.3.8-py2.py3-none-any.whl (25 kB)
Collecting pytz
Downloading pytz-2020.1-py2.py3-none-any.whl (510 kB)
|████████████████████████████████| 510 kB 772 kB/s
Collecting aniso8601>=0.82
Downloading aniso8601-8.0.0-py2.py3-none-any.whl (43 kB)
|████████████████████████████████| 43 kB 232 kB/s
Collecting Flask>=0.8
Using cached Flask-1.1.2-py2.py3-none-any.whl (94 kB)
Collecting six>=1.3.0
Downloading six-1.14.0-py2.py3-none-any.whl (10 kB)
Collecting Jinja2>=2.10.1
Downloading Jinja2-2.11.2-py2.py3-none-any.whl (125 kB)
|████████████████████████████████| 125 kB 248 kB/s
Collecting click>=5.1
Downloading click-7.1.2-py2.py3-none-any.whl (82 kB)
|████████████████████████████████| 82 kB 28 kB/s
Collecting itsdangerous>=0.24
Downloading itsdangerous-1.1.0-py2.py3-none-any.whl (16 kB)
Collecting Werkzeug>=0.15
Downloading Werkzeug-1.0.1-py2.py3-none-any.whl (298 kB)
|████████████████████████████████| 298 kB 99 kB/s
Collecting MarkupSafe>=0.23
Downloading MarkupSafe-1.1.1-cp37-cp37m-macosx_10_6_intel.whl (18 kB)
Installing collected packages: pytz, aniso8601, MarkupSafe, Jinja2, click, itsdangerous, Werkzeug, Flask, six, Flask-RESTful
Packages installed here will not affect the global Python installation. Virtualenv does not create every file needed to get a whole new python environment. It uses links to global environment files instead in order to save disk space and therefore, speeds up your virtualenv. There must already have an active python environment installed on your system.
To install packages/modules for your isolated environment, you can also create a text file which include all the packages/tools needed with their versions and do:
pip3 install -r requirements.txt
In order to deactivate the current environment you can type:
deactivate
You can verify quickly you are in the environment by running which python3 or which pip3 which will return the path of the python executable in the environment if all went well:
(venv) (base) Arat-MacBook-Pro:REST APIs with Flask and Python mustafamuratarat$ which pip3
/Users/mustafamuratarat/Desktop/REST APIs with Flask and Python/venv/bin/pip3
(venv) (base) Arat-MacBook-Pro:REST APIs with Flask and Python mustafamuratarat$ which python3
/Users/mustafamuratarat/Desktop/REST APIs with Flask and Python/venv/bin/python3
To remove an environment, make sure you have deactivated it, then cd into the environment directory and type
sudo rm -rf <my_env_name>