Python2转换成Python3

Python2转换成Python3 - 迷途小书童的Note迷途小书童的Note

• windows 11 64bit

Python2 和 Python3 在语法和某些模块的使用上是有一些差别的，对于一些用 python2 编写的历史项目，要重新启用它们，2to3 是一个不错的转换工具，也是官方提供的工具，不需要安装，可靠性也比较高，它读取 Python 2.x 源代码并应用一系列修复程序将其转换为有效的 Python 3.x 代码。

可以在终端中查看命令支持的所有参数

1. (base) PS C:\Users\xgx> 2to3.exe -h
2. Usage: 2to3 [options] file|dir ...
3. Options:
4. -h, --help show this help message and exit
5. -d, --doctests_only Fix up doctests only
6. -f FIX, --fix=FIX Each FIX specifies a transformation; default: all
7. -j PROCESSES, --processes=PROCESSES
8. Run 2to3 concurrently
9. -x NOFIX, --nofix=NOFIX
10. Prevent a transformation from being run
11. -l, --list-fixes List available transformations
12. -p, --print-function Modify the grammar so that print() is a function
13. -e, --exec-function Modify the grammar so that exec() is a function
14. -v, --verbose More verbose logging
15. --no-diffs Don't show diffs of the refactoring
16. -w, --write Write back modified files
17. -n, --nobackups Don't write backups for modified files
18. -o OUTPUT_DIR, --output-dir=OUTPUT_DIR
19. Put output files in this directory instead of
20. overwriting the input files. Requires -n.
21. -W, --write-unchanged-files
22. Also write files even if no changes were required
23. (useful with --output-dir); implies -w.
24. --add-suffix=ADD_SUFFIX
25. Append this string to all output filenames. Requires
26. -n if non-empty. ex: --add-suffix='3' will generate
27. .py3 files.

下面看一个具体的示例，这是 python2 编写的代码，保存成文件 test.py

1. def greet(name):
2. print "Hello, {0}!".format(name)
3. print "What's your name?"
4. name = raw_input()
5. greet(name)

执行转换命令

1. 2to3.exe -w test.py

可以看到，转换过程中会输出2个版本的差异，然后将转换后的内容写入原文件中(即覆盖)，而原文件内容会存放在 test.py.bak 中进行备份

1. (base) PS C:\Users\xgx\Desktop> 2to3.exe -w test.py
2. RefactoringTool: Skipping optional fixer: buffer
3. RefactoringTool: Skipping optional fixer: idioms
4. RefactoringTool: Skipping optional fixer: set_literal
5. RefactoringTool: Skipping optional fixer: ws_comma
6. RefactoringTool: Refactored test.py
7. --- test.py (original)
8. +++ test.py (refactored)
9. @@ -1,5 +1,5 @@
10. def greet(name):
11. - print "Hello, {0}!".format(name)
12. -print "What's your name?"
13. -name = raw_input()
14. + print("Hello, {0}!".format(name))
15. +print("What's your name?")
16. +name = input()
17. greet(name)
18. RefactoringTool: Files that were modified:
19. RefactoringTool: test.py

如果是文件夹批量转换，命令直接跟上源码文件夹即可，如

1. 2to3.exe -w D:\project

指定输出文件夹，使用 -o 参数；不想要 python2 的备份，使用 -n 参数

• https://docs.python.org/3/library/2to3.html