As of flask 0.7 (June 28th, 2011), a
__version__ attribute can be found on the flask module.
>> import flask >> flask.__version__
Keep in mind that because prior to flask 0.7 there was no
__version__ attribute, the preceding code will result in an attribute error on those older versions.
For versions older than flask 0.7, you might be able to determine it using pkg_resources as shown below:
>>> import pkg_resources >>> pkg_resources.get_distribution('flask').version '0.6.1'
This won't work 100% though. It depends on the user having the pkg_resources library installed (it might come by default with a Linux distribution's python installation, but since it's not part of the standard library you can't be positive), and also that the user installed flask in a way that pkg_resources can find it (for example, just copying the full flask source code into your directory puts it out of the range of pkg_resources).
Via the python interpreter.
>> import flask >> flask.__version__ '0.7.2'
If flask was installed via pip or easy_install, you can always use the 'pip freeze' command.