Flask – Environment

Prerequisite

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.

Install virtualenv for development environment

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 under C:/pythonX/scripts path.Here X is the version name of Python.

pip install virtualenv

The output should be like this −

Collecting virtualenv
  Downloading virtualenv-15.0.1-py2.py3-none-any.whl (1.8MB)
    100% |################################| 1.8MB 204kB/s
Installing collected packages: virtualenv
Successfully installed virtualenv-15.0.1

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 −

venv/bin/activate

On Windows, following can be used −

venv\scripts\activate

We are now ready to install Flask in this environment.

pip install Flask

The output should be like this −

Collecting Flask
  Downloading Flask-0.10.1.tar.gz (544kB)
    100% |################################| 544kB 410kB/s
Collecting Werkzeug>=0.7 (from Flask)
  Downloading Werkzeug-0.11.4-py2.py3-none-any.whl (305kB)
    100% |################################| 307kB 531kB/s
Collecting Jinja2>=2.4 (from Flask)
  Downloading Jinja2-2.8-py2.py3-none-any.whl (263kB)
    100% |################################| 266kB 935kB/s
Collecting itsdangerous>=0.21 (from Flask)
  Downloading itsdangerous-0.24.tar.gz (46kB)
    100% |################################| 49kB 1.6MB/s
Collecting MarkupSafe (from Jinja2>=2.4->Flask)
  Downloading MarkupSafe-0.23.tar.gz
Installing collected packages: Werkzeug, MarkupSafe, Jinja2, itsdangerous, Flask
  Running setup.py install for MarkupSafe
  Running setup.py install for itsdangerous
  Running setup.py install for Flask
Successfully installed Flask-0.10.1 Jinja2-2.8 MarkupSafe-0.23 Werkzeug-0.11.4 itsdangerous-0.24

The above command can be run directly, without virtual environment for system-wide installation.