2to3

Show changes without applying

$ 2to3 [script.py]

$ 2to3 -w [script.py]

$ 2to3 -w [directory/]

$ 2to3 -f [print] -f [import] [script.py]

$ 2to3 -l

$ 2to3 -w -n [script.py]

2to3 [options] file|directory

2to3 is an automated Python 2 to Python 3 code translator. It parses Python 2 source code and applies "fixers" that transform incompatible syntax and library calls to their Python 3 equivalents.
Common transformations include:
- print statement to print() function
- unicode to str, str to bytes
- raw_input() to input()
- Iterator methods (.iteritems() to .items())
- except Exception, e to except Exception as e
- Library renames (urllib, ConfigParser, etc.)
2to3 handles most mechanical changes but may require manual review for semantic differences between Python 2 and 3.

-w, --write

Write changes to files

Don't create .bak backup files

Apply specific fixer

Exclude specific fixer

List available fixers

Assume print function is already imported

Run in parallel with n processes

Write converted files to directory

More verbose output

2to3 makes syntactic changes but cannot handle all differences. Code behavior may still differ, especially around:
- String/bytes handling
- Integer division
- Dictionary ordering (pre-Python 3.7)
- Unicode text processing
Running -w without -n creates .bak files that may clutter version control.
Python 2 reached end-of-life in January 2020. For major projects, consider modern porting tools like python-modernize or futurize.

python(1), python3(1), pip(1)