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How to Download and Use 2to3.py for Automated Python 2 to 3 Code Translation


How to Download and Use 2to3.py to Convert Python 2 Code to Python 3




If you are a Python developer, you may have encountered the challenge of migrating your code from Python 2 to Python 3. Python 2 is no longer supported since January 2020, and Python 3 offers many improvements and new features that make it more powerful, expressive, and modern. However, there are some significant differences between the two versions that may prevent your code from running smoothly on both. That's where 2to3.py comes in handy.


What is 2to3.py and Why Do You Need It?




2to3.py 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. It is part of the lib2to3 library, which provides a generic framework for source-to-source transformations. 2to3.py can handle most of the common syntax and semantic changes between the two versions, such as print statements, integer division, exception handling, Unicode literals, and more. It can also refactor doctests, which are interactive Python sessions embedded in docstrings or comments.




download 2to3.py



You need 2to3.py if you have legacy Python 2 code that you want to migrate to Python 3, or if you want to learn how to write compatible code for both versions. Although there are some tools and techniques that can help you write code that runs on both Python 2 and Python 3 (such as six, future, and __future__ imports), they may not cover all the cases or may introduce some overhead or complexity. Using 2to3.py can help you make a clean transition to Python 3 and take advantage of its new features and benefits.


How to Download 2to3.py




2to3.py is usually installed with the Python interpreter as a script. You can find it in the Scripts directory of your Python installation (e.g. C:\Python39\Scripts on Windows). You can also run it as a module by using the -m flag (e.g. `python -m lib2to3`).


You can also find 2to3.py in the Tools/scripts directory of the Python root. You can download the latest version of Python from the official website and extract the zip file to access the script. Alternatively, you can clone the Python repository from GitHub and navigate to the Tools/scripts folder.


Another option is to install 2to3.py with pip by running `pip install 2to3`. This will download and install the script from PyPI, the Python Package Index. You can then run it from any directory by typing `2to3` in your console.


How to Use 2to3.py




To use 2to3.py, you need to open a console (cmd if Windows) and execute the script with the appropriate arguments . The basic arguments are a list of files or directories to transform. For example, if you have a file called example.py that contains Python 2 code, you can run `python 2to3.py example.py` to see what changes would be made to convert it to Python 3. The output will be a diff against the original source file, showing the lines that would be added (+) or deleted (-). For example:


$ python 2to3.py example.py RefactoringTool: Skipping implicit fixer: buffer RefactoringTool: Skipping implicit fixer: idioms RefactoringTool: Skipping implicit fixer: set_literal RefactoringTool: Skipping implicit fixer: ws_comma --- example.py (original) +++ example.py (refactored) @@ -1,7 +1,7 @@ # A simple example of Python 2 code -print "Hello, world!" +print("Hello, world!") -def greet(name): - print "Hello, %s!" % name +def greet(name):+ + print("Hello, %s!" % name) greet("Alice") -greet name="Bob" +greet(name="Bob")


If you want to apply the changes to the source file, you need to use the -w flag, which enables writeback. This will modify the original file and create a backup with a .bak extension (unless you also use the -n flag, which disables backup). For example:


$ python 2to3.py -w example.py RefactoringTool: Skipping implicit fixer: buffer RefactoringTool: Skipping implicit fixer: idioms RefactoringTool: Skipping implicit fixer: set_literal RefactoringTool: Skipping implicit fixer: ws_comma RefactoringTool: Refactored example.py --- example.py (original) +++ example.py (ref actored) @@ -1,7 +1,7 @@ # A simple example of Python 2 code -print "Hello, world!" +print("Hello, world!") -def greet(name): - print "Hello, %s!" % name +def greet(name):+ + print("Hello, %s!" % name) greet("Alice") -greet name="Bob" +greet(name="Bob") RefactoringTool: Files that need to be modified: RefactoringTool: example.py


You can also specify a directory instead of a file, and 2to3.py will recursively convert all the .py files in that directory. You can use the --output-dir option to specify a different directory for the output files, instead of overwriting the original ones. For example:


$ python 2to3.py --output-dir=python3-version/mycode -W -n python2-version/mycode RefactoringTool: Skipping implicit fixer: buffer RefactoringTool: Skipping implicit fixer: idioms RefactoringTool: Skipping implicit fixer: set_literal RefactoringTool: Skipping implicit fixer: ws_comma RefactoringTool: Refactored python2-version/mycode/example.py --- python2-version/mycode/example.py (original) +++ python3-version/mycode/example.py (refactored) @@ -1,7 +1,7 @@ # A simple example of Python 2 code -print "Hello, world!" +print("Hello, world!") -def greet(name): - print "Hello, %s!" % name +def greet(name):+ + print("Hello, %s!" % name) greet("Alice") -greet name="Bob" +greet(name="Bob") RefactoringTool: Files that were modified: RefactoringTool: python2-version/mycode/example.py


2to3.py has many options and flags that you can use to customize the conversion process. Here are some of the most useful ones:


How to install 2to3 on Windows


Python 2to3 command line tool


2to3 PyPI package download


Python 2to3 automated code translation


2to3 fixers and options


Convert Python 2.x to 3.x with 2to3


2to3 deprecated in Python 3.11


Run 2to3 on a directory of Python files


Enable doctest refactoring with 2to3


Write custom fixers for 2to3


2to3 example.py diff output


2to3 -w flag to write changes back


List available fixers with 2to3 -l


Run specific fixers with 2to3 -f


Disable fixers with 2to3 -x


Run all default fixers with 2to3 -f all


Run idioms fixer with 2to3 -f idioms


Address warnings from 2to3


Compare 2to3 and six for Python compatibility


Alternatives to 2to3 for Python migration


Use 2to3 in a virtual environment


Integrate 2to3 with an IDE or editor


Troubleshoot errors from 2to3


Test code after running 2to3


Review changes made by 2to3


Backup files before using 2to3


Undo changes made by 2to3


Use git to track changes from 2to3


Best practices for using 2to3


Benefits and drawbacks of using 2to3


How to run 2to3 on multiple files at once


How to run 2to3 on a reST document with doctests


How to run 2to3 on a Jupyter notebook


How to run 2to3 on a Django project


How to run 2to3 on a Flask app


How to run 2to3 on a PyQt GUI


How to run 2to3 on a Tkinter GUI


How to run 2to3 on a Scrapy spider


How to run 2to3 on a NumPy array


How to run 2to3 on a pandas dataframe


How to run 2to3 on a matplotlib plot


How to run 2to3 on a seaborn plot


How to run 2to3 on a SciPy function


How to run 2to3 on a sklearn model


How to run 2to3 on a TensorFlow graph


How to run 2to3 on a Keras model


How to run 2to3 on a PyTorch model


How to run 2to3 on a NLTK corpus


How to run 2to3 on a spaCy pipeline


  • The -l flag lists all available fixers. Fixers are the modules that perform the actual transformations on the code. There are over 40 fixers in 2to3.py, covering various aspects of Python syntax and semantics. For example:



$ python 2to3.py -l Available transformations for the -f/--fix option: apply asserts basestring buffer callable dict except exec execfile exitfunc filter funcattrs future getcwdu has_key idioms import imports2 imports3 index input intern isinstance itertools_imports itertools_methods keys long map metaclass methodattrs ne next nonzero numliterals operator parenthesize print raise raw_input reduce reload renames repr set_literal standarderror sys_exc throw tuple_params types unicode urllib ws_comma xrange xreadlines zip


  • The -f flag specifies an explicit set of fixers to run. You can use this option to limit the scope of the conversion or to focus on specific issues. For example, if you only want to convert the print statements and the integer division, you can run `python 2to3.py -f print -f division example.py`.



  • The -x flag explicitly disables a fixer. You can use this option to exclude some fixers that you don't want to apply or that may cause problems. For example, if you want to keep the old-style classes and not use the new-style classes, you can run `python 2to3.py -x class example.py`.



  • The -d flag enables refactoring of doctests. Doctests are interactive Python sessions embedded in docstrings or comments, and they may contain Python 2 code that needs to be converted as well. By default, 2to3.py does not touch doctests, but you can use this flag to include them in the conversion. For example, if you have a file called test.py that contains doctests, you can run `python 2to3.py -d test.py` to see the changes.



The -v flag enables output of more info


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