Python2到Python3代码的转换工具2to3.py

之前一直遇到Python2代码转到Python3代码的需求，最近才知道Python官方就有一个转换工具：2to3.py。
无论是Python官网下载安装的python还是利用Anaconda安装，目录都在{Python_HOME}\Tools\scripts里面。运行 2to3.py 脚本，打印如下：

python 2to3.py --helpUsage: 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  -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

假设我在E:\pycode目录下有个py2.py文件，代码如下：

print 'test'

我想把上面的代码改成python3版本的。、
应该先cmd进入{Python_HOME}\Tools\scripts目录，然后执行如下：

python 2to3.py -w E:\pycode\py2.py

执行整个流程如下：

D:\Anaconda3\Tools\scripts>python 2to3.py -w E:\pycode\py2.pyRefactoringTool: Skipping optional fixer: bufferRefactoringTool: Skipping optional fixer: idiomsRefactoringTool: Skipping optional fixer: set_literalRefactoringTool: Skipping optional fixer: ws_commaRefactoringTool: Refactored E:\pycode\py2.py--- E:\pycode\py2.py    (original)+++ E:\pycode\py2.py    (refactored)@@ -1 +1 @@-print 'test'+print('test')RefactoringTool: Files that were modified:RefactoringTool: E:\pycode\py2.py

然后我们可以看到，在E:\pycode目录下多了一个py2.py.bak文件，这是原来的py2.py文件备份。
查看py2.py，内容已被修改为：

print('test')