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95 lines
3.9 KiB
95 lines
3.9 KiB
=====================================================
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Supporting both Python 2 and Python 3 with Setuptools
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=====================================================
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Starting with Distribute version 0.6.2 and Setuptools 0.7, the Setuptools
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project supported Python 3. Installing and
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using setuptools for Python 3 code works exactly the same as for Python 2
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code.
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Setuptools provides a facility to invoke 2to3 on the code as a part of the
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build process, by setting the keyword parameter ``use_2to3`` to True, but
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the Setuptools strongly recommends instead developing a unified codebase
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using `six <https://pypi.org/project/six/>`_,
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`future <https://pypi.org/project/future/>`_, or another compatibility
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library.
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Using 2to3
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==========
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Setuptools attempts to make the porting process easier by automatically
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running
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2to3 as a part of running tests. To do so, you need to configure the
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setup.py so that you can run the unit tests with ``python setup.py test``.
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See :ref:`test` for more information on this.
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Once you have the tests running under Python 2, you can add the use_2to3
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keyword parameters to setup(), and start running the tests under Python 3.
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The test command will now first run the build command during which the code
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will be converted with 2to3, and the tests will then be run from the build
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directory, as opposed from the source directory as is normally done.
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Setuptools will convert all Python files, and also all doctests in Python
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files. However, if you have doctests located in separate text files, these
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will not automatically be converted. By adding them to the
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``convert_2to3_doctests`` keyword parameter Setuptools will convert them as
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well.
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By default, the conversion uses all fixers in the ``lib2to3.fixers`` package.
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To use additional fixers, the parameter ``use_2to3_fixers`` can be set
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to a list of names of packages containing fixers. To exclude fixers, the
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parameter ``use_2to3_exclude_fixers`` can be set to fixer names to be
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skipped.
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An example setup.py might look something like this::
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from setuptools import setup
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setup(
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name='your.module',
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version='1.0',
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description='This is your awesome module',
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author='You',
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author_email='your@email',
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package_dir={'': 'src'},
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packages=['your', 'you.module'],
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test_suite='your.module.tests',
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use_2to3=True,
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convert_2to3_doctests=['src/your/module/README.txt'],
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use_2to3_fixers=['your.fixers'],
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use_2to3_exclude_fixers=['lib2to3.fixes.fix_import'],
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)
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Differential conversion
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-----------------------
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Note that a file will only be copied and converted during the build process
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if the source file has been changed. If you add a file to the doctests
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that should be converted, it will not be converted the next time you run
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the tests, since it hasn't been modified. You need to remove it from the
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build directory. Also if you run the build, install or test commands before
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adding the use_2to3 parameter, you will have to remove the build directory
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before you run the test command, as the files otherwise will seem updated,
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and no conversion will happen.
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In general, if code doesn't seem to be converted, deleting the build directory
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and trying again is a good safeguard against the build directory getting
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"out of sync" with the source directory.
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Distributing Python 3 modules
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=============================
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You can distribute your modules with Python 3 support in different ways. A
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normal source distribution will work, but can be slow in installing, as the
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2to3 process will be run during the install. But you can also distribute
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the module in binary format, such as a binary egg. That egg will contain the
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already converted code, and hence no 2to3 conversion is needed during install.
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Advanced features
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=================
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If you don't want to run the 2to3 conversion on the doctests in Python files,
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you can turn that off by setting ``setuptools.use_2to3_on_doctests = False``.
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