Neat way to port nonpolyglot code from Py2 to Py3

Question

In many of my python modules, I am using

from itertools import izip_longest

But now I am moving my codebase to Py3 (compatible with Py2 at the sa

Answer 1

I see your other question got closed so I'll post here. So, there's a couple files, and naming is important!

fixer.py

#!/usr/bin/env python3
# you'll need 2to3 and python-modernize installed
from __future__ import absolute_import
import sys
from lib2to3.main import main
import libmodernize

sys.path.append(".")
sys.exit(main('fixers'))

fixers/fix_iziplongest.py

from lib2to3 import fixer_base
import libmodernize

class FixIziplongest(fixer_base.BaseFix):
    PATTERN = """
    power< 'izip_longest' trailer< '(' any* ')' > >
    | import_from< 'from' 'itertools' 'import' 'izip_longest' >
    """

    # This function is only called on matches to our pattern, which should
    # be usage of izip_longest, and the itertools import
    def transform(self, node, results):
        # add the new import (doesn't matter if we do this multiple times
        libmodernize.touch_import('itertools_compat', 'zip_longest', node)
        # remove the old import
        if node.type == syms.import_from:
            node.parent.remove()
            return node
        
        # rename to izip_longest
        node.children[0].value = 'zip_longest'
        return node

Usage is the same as 2to3 - python ./fixer.py -f iziplongest file_to_fix.py (more flags if you want it to apply changes, that'll just show the diff) So, what this does is it would covert this:

from itertools import izip_longest
for x in izip_longest(a, b):
     print(x)

To this:

from itertools_compat import zip_longest
for x in zip_longest(a, b):
     print(x)