python2代码升级到python3工具

 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

   -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='' will generate

                         .py3 files.