.. _installation: Installation ============ Python Version -------------- We recommend using the latest version of Python 3. Flask supports Python 3.3 and newer, Python 2.6 and newer, and PyPy. Dependencies ------------ These distributions will be installed automatically when installing Flask. * `Werkzeug`_ implements WSGI, the standard Python interface between applications and servers. * `Jinja`_ is a template language that renders the pages your application serves. * `MarkupSafe`_ comes with Jinja. It escapes untrusted input when rendering templates to avoid injection attacks. * `ItsDangerous`_ securely signs data to ensure its integrity. This is used to protect Flask's session cookie. * `Click`_ is a framework for writing command line applications. It provides the ``flask`` command and allows adding custom management commands. .. _Werkzeug: http://werkzeug.pocoo.org/ .. _Jinja: http://jinja.pocoo.org/ .. _MarkupSafe: https://pypi.python.org/pypi/MarkupSafe .. _ItsDangerous: https://pythonhosted.org/itsdangerous/ .. _Click: http://click.pocoo.org/ Optional dependencies ~~~~~~~~~~~~~~~~~~~~~ These distributions will not be installed automatically. Flask will detect and use them if you install them. * `Blinker`_ provides support for :ref:`signals`. * `SimpleJSON`_ is a fast JSON implementation that is compatible with Python's ``json`` module. It is preferred for JSON operations if it is installed. .. _Blinker: https://pythonhosted.org/blinker/ .. _SimpleJSON: https://simplejson.readthedocs.io/ Virtual environments -------------------- Use a virtual environment to manage the dependencies for your project, both in development and in production. What problem does a virtual environment solve? The more Python projects you have, the more likely it is that you need to work with different versions of Python libraries, or even Python itself. Newer versions of libraries for one project can break compatibility in another project. Virtual environments are independent groups of Python libraries, one for each project. Packages installed for one project will not affect other projects or the operating system's packages. Python 3 comes bundled with the :mod:`venv` module to create virtual environments. If you're using a modern version of Python, you can continue on to the next section. If you're using Python 2, see :ref:`install-install-virtualenv` first. .. _install-create-env: Create an environment ~~~~~~~~~~~~~~~~~~~~~ Create a project folder and a :file:`venv` folder within: .. code-block:: sh mkdir myproject cd myproject python3 -m venv venv On Windows: .. code-block:: bat py -3 -m venv venv If you needed to install virtualenv because you are on an older version of Python, use the following command instead: .. code-block:: sh virtualenv venv On Windows: .. code-block:: bat \Python27\Scripts\virtualenv.exe venv Activate the environment ~~~~~~~~~~~~~~~~~~~~~~~~ Before you work on your project, activate the corresponding environment: .. code-block:: sh . venv/bin/activate On Windows: .. code-block:: bat venv\Scripts\activate Your shell prompt will change to show the name of the activated environment. Install Flask ------------- Within the activated environment, use the following command to install Flask: .. code-block:: sh pip install Flask Living on the edge ~~~~~~~~~~~~~~~~~~ If you want to work with the latest Flask code before it's released, install or update the code from the master branch: .. code-block:: sh pip install -U https://github.com/pallets/flask/archive/master.tar.gz .. _install-install-virtualenv: Install virtualenv ------------------ If you are using Python 2, the venv module is not available. Instead, install `virtualenv`_. On Linux, virtualenv is provided by your package manager: .. code-block:: sh # Debian, Ubuntu sudo apt-get install python-virtualenv # CentOS, Fedora sudo yum install python-virtualenv # Arch sudo pacman -S python-virtualenv If you are on Mac OS X or Windows, download `get-pip.py`_, then: .. code-block:: sh sudo python2 Downloads/get-pip.py sudo python2 -m pip install virtualenv On Windows, as an administrator: .. code-block:: bat \Python27\python.exe Downloads\get-pip.py \Python27\python.exe -m pip install virtualenv Now you can continue to :ref:`install-create-env`. .. _virtualenv: https://virtualenv.pypa.io/ .. _get-pip.py: https://bootstrap.pypa.io/get-pip.py