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.. _python3-support:
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Python 3 Support
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================
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Flask and all of its dependencies support Python 3 so you can in theory
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start working on it already. There are however a few things you should be
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aware of before you start using Python 3 for your next project.
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Requirements
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------------
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If you want to use Flask with Python 3 you will need to use Python 3.3 or
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higher. 3.2 and older are *not* supported.
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In addition to that you need to use the latest and greatest versions of
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`itsdangerous`, `Jinja2` and `Werkzeug`.
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API Stability
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-------------
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Some of the decisions made in regards to unicode and byte untilization on
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Python 3 make it hard to write low level code. This mainly affects WSGI
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middlewares and interacting with the WSGI provided information. Werkzeug
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wraps all that information in high-level helpers but some of those were
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specifically added for the Python 3 support and are quite new.
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A lot of the documentation out there on using WSGI leaves out those
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details as it was written before WSGI was updated to Python 3. While the
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API for Werkzeug and Flask on Python 2.x should not change much we cannot
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guarantee that this won't happen on Python 3.
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Few Users
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---------
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Python 3 currently has less than 1% of the users of Python 2 going by PyPI
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download stats. As a result many of the problems you will encounter are
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probably hard to search for on the internet if they are Python 3 specific.
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Small Ecosystem
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---------------
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The majority of the Flask extensions, all of the documentation and the
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vast majority of the PyPI provided libraries do not support Python 3 yet.
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Even if you start your project with knowing that all you will need is
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supported by Python 3 you don't know what happens six months from now. If
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you are adventurous you can start porting libraries on your own, but that
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is nothing for the faint of heart.
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Recommendations
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---------------
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Unless you are already familiar with the differences in the versions we
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recommend sticking to current versions of Python until the ecosystem
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caught up.
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The majority of the upgrade pain is in the lower-level libararies like
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Flask and Werkzeug and not in the actual high-level application code. For
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instance all of the Flask examples that are in the Flask repository work
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out of the box on both 2.x and 3.x and did not require a single line of
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code changed.
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