【linux/windows】python2代码转python3-工具2to3

尽管现在有很多项目基于python2开发，但越来越多的项目以python3开发，而且越来越多的包开始不支持python2，就拿ubuntu系列版本来说，ubuntu20.04源库没有python-pip，或者做web开发的django框架3.0来说，直接python3，但项目肯定不可能直接重写，幸运的是不管win系统还是linux下都提供了对应的版本转换工具，只需简单执行相关命令，即可完成python2转python3。

1.windows下转换

在我们安装的python文件目录下，最好在官网下载zip包，解压后放置任何位置，同时设置环境变量，保证在命令行下运行python可以运行，当然嫌麻烦也可以下载那种一路next的版本，环境变量默认帮你设置好的。

假定上述工作你已完成的情况下，接下来打开python的安装目录，比如以下是我自己的目录及文件：

注意2to3.py，通过此文件就可以完成版本转换，下面是使用实例。

# 查看哪些是需要更改的
python 2to3.py test.py

# py2转py3
python 2to3.py -w test.py

# 批量转换或查看更改部分
python 2to3.py [-w] ./

2.linux下的转换-ubuntu18.04

在ubuntu下，直接有这样一个二进制的命令2to3，可以直接运行这个命令更改相关代码。

# 查看命令
root@ubuntu:~# ls -l  /usr/bin/ | grep 2to3
-rwxr-xr-x 1 root root           96 Feb 27 23:10 2to3-2.7

# 查看帮助
root@ubuntu:~# 2to3-2.7 --help
Usage: 2to3 [options] file|dir ...

Options:
  -h, --help            show this help message and exit
  -d, --doctests_only   Fix up doctests only
  -f FIX, --fix=FIX     Each FIX specifies a transformation; default: all
  -j PROCESSES, --processes=PROCESSES
                        Run 2to3 concurrently
  -x NOFIX, --nofix=NOFIX
                        Prevent a transformation from being run
  -l, --list-fixes      List available transformations
  -p, --print-function  Modify the grammar so that print() is a function
  -v, --verbose         More verbose logging
  --no-diffs            Don't show diffs of the refactoring
  -w, --write           Write back modified files # 使用后，后将文件转换python3，同时多出后缀.bak的备份文件，python2版本
  -n, --nobackups       Don't write backups for modified files
  -o OUTPUT_DIR, --output-dir=OUTPUT_DIR
                        Put output files in this directory instead of
                        overwriting the input files.  Requires -n.
  -W, --write-unchanged-files
                        Also write files even if no changes were required
                        (useful with --output-dir); implies -w.
  --add-suffix=ADD_SUFFIX
                        Append this string to all output filenames. Requires
                        -n if non-empty.  ex: --add-suffix='3' will generate
                        .py3 files.

# 查看需要更改处
root@ubuntu:~/test2to3# 2to3-2.7 pkg/p_demo.py.bak
RefactoringTool: Skipping optional fixer: buffer
RefactoringTool: Skipping optional fixer: idioms
RefactoringTool: Skipping optional fixer: set_literal
RefactoringTool: Skipping optional fixer: ws_comma
RefactoringTool: Refactored pkg/p_demo.py.bak
--- pkg/p_demo.py.bak   (original)
+++ pkg/p_demo.py.bak   (refactored)
@@ -1,2 +1,2 @@
 #!/usr/bin/python
-print "p_demo file"
+print("p_demo file")
RefactoringTool: Files that need to be modified:
RefactoringTool: pkg/p_demo.py.bak

# py2 -> py3
root@ubuntu:~/test2to3# 2to3-2.7 pkg/p_demo.py.bak -w
RefactoringTool: Skipping optional fixer: buffer
RefactoringTool: Skipping optional fixer: idioms
RefactoringTool: Skipping optional fixer: set_literal
RefactoringTool: Skipping optional fixer: ws_comma
RefactoringTool: Refactored pkg/p_demo.py.bak
--- pkg/p_demo.py.bak   (original)
+++ pkg/p_demo.py.bak   (refactored)
@@ -1,2 +1,2 @@
 #!/usr/bin/python
-print "p_demo file"
+print("p_demo file")
RefactoringTool: Files that were modified:
RefactoringTool: pkg/p_demo.py.bak

# 也可以直接对目录进行操作
root@ubuntu:~/test2to3# 2to3-2.7 [-w] ./
RefactoringTool: Skipping optional fixer: buffer
RefactoringTool: Skipping optional fixer: idioms
RefactoringTool: Skipping optional fixer: set_literal
RefactoringTool: Skipping optional fixer: ws_comma
RefactoringTool: No changes to ./pkg/p_demo.py
RefactoringTool: No changes to ./proj/pro_demo2.py
RefactoringTool: No changes to ./tools/t_demo3.py
RefactoringTool: Files that need to be modified:
RefactoringTool: ./pkg/p_demo.py
RefactoringTool: ./proj/pro_demo2.py
RefactoringTool: ./tools/t_demo3.py

以上是不同系统下使用2to3工具转换python版本，希望对你有用。