Python 2.6 or higher is usually required for installation of Flask. Although Flask and its dependencies work well with Python 3 (Python 3.3 onwards), many Flask extensions do not support it properly. Hence, it is recommended that Flask should be installed on Python 2.7.
virtualenv is a virtual Python environment builder. It helps a user to create multiple Python environments side-by-side. Thereby, it can avoid compatibility issues between the different versions of the libraries.
The following command installs virtualenv
pip install virtualenv
This command needs administrator privileges. Add sudo before pip on Linux/Mac OS. If you are on Windows, log in as Administrator. On Ubuntu virtualenv may be installed using its package manager.
Sudo apt-get install virtualenv
Once installed, new virtual environment is created in a folder.
mkdir newproj cd newproj virtualenv venv
To activate corresponding environment, on Linux/OS X, use the following −
On Windows, following can be used
We are now ready to install Flask in this environment.
pip install Flask
The above command can be run directly, without virtual environment for system-wide installation.