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Diffstat (limited to 'Doc/library/2to3.rst')
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1 files changed, 35 insertions, 14 deletions
diff --git a/Doc/library/2to3.rst b/Doc/library/2to3.rst index 99749b3..e8ea861 100644 --- a/Doc/library/2to3.rst +++ b/Doc/library/2to3.rst @@ -7,15 +7,21 @@ 2to3 is a Python program that reads Python 2.x source code and applies a series of *fixers* to transform it into valid Python 3.x code. The standard library -contains a rich set of fixers that will handle almost all code. It is, however, -possible to write your own fixers. +contains a rich set of fixers that will handle almost all code. 2to3 supporting +library :mod:`lib2to3` is, however, a flexible and generic library, so it is +possible to write your own fixers for 2to3. :mod:`lib2to3` could also be +adapted to custom applications in which Python code needs to be edited +automatically. Using 2to3 ---------- -2to3 can be run with a list of files to transform or a directory to recursively -traverse looking for files with the ``.py`` extension. +2to3 will usually be installed with the Python interpreter as a script. It is +also located in the :file:`Tools/scripts` directory of the Python root. + +2to3's basic arguments are a list of files or directories to transform. The +directories are to recursively traversed for Python sources. Here is a sample Python 2.x source file, :file:`example.py`:: @@ -29,13 +35,14 @@ It can be converted to Python 3.x code via 2to3 on the command line:: $ 2to3 example.py -A diff against the original source file will be printed. 2to3 can also write -the needed modifications right back to the source file. (A backup of the -original file will also be made.) This is done with the :option:`-w` flag:: +A diff against the original source file is printed. 2to3 can also write the +needed modifications right back to the source file. (Of course, a backup of the +original is also be made.) Writing the changes back is enabled with the +:option:`-w` flag:: $ 2to3 -w example.py -:file:`example.py` will now look like this:: +After transformation, :file:`example.py` looks like this:: def greet(name): print("Hello, {0}!".format(name)) @@ -43,10 +50,10 @@ original file will also be made.) This is done with the :option:`-w` flag:: name = input() greet(name) -Comments and and exact indentation will be preserved throughout the translation +Comments and and exact indentation are preserved throughout the translation process. -By default, 2to3 will run a set of predefined fixers. The :option:`-l` flag +By default, 2to3 runs a set of predefined fixers. The :option:`-l` flag lists all avaible fixers. An explicit set of fixers to run can be given by use of the :option:`-f` flag. The following example runs only the ``imports`` and ``has_key`` fixers:: @@ -54,16 +61,30 @@ of the :option:`-f` flag. The following example runs only the ``imports`` and $ 2to3 -f imports -f has_key example.py Some fixers are *explicit*, meaning they aren't run be default and must be -listed on the command line. Here, in addition to the default fixers, the -``idioms`` fixer is run:: +listed on the command line to be run. Here, in addition to the default fixers, +the ``idioms`` fixer is run:: $ 2to3 -f all -f idioms example.py -Notice how ``all`` enables all default fixers. +Notice how passing ``all`` enables all default fixers. Sometimes 2to3 will find will find a place in your source code that needs to be changed, but 2to3 cannot fix automatically. In this case, 2to3 will print a -warning beneath the diff for a file. +warning beneath the diff for a file. You should address the warning in order to +have compliant 3.x code. + +2to3 can also refactor doctests. To enable this mode, use the :option:`-d` +flag. Note that *only* doctests will be refactored. + +The :option:`-v` option enables the output of more information on the +translation process. + +When the :option:`-p` is passed to it, 2to3 treats ``print`` as a function +instead of a statement. This is useful when ``from __future__ import +print_function`` is being used. If this option is not given, the print fixer +will surround print calls in an extra set of parentheses because it cannot +differentiate between the and print statement with parentheses (such as ``print +("a" + "b" + "c")``) and a true function call. :mod:`lib2to3` - 2to3's library |