OrderedDict vs. dict

py2py3odict.py

from collections import OrderedDict

# This will raise a RuntimeError in python3, but will work
# in python2.
regular_dict = dict(a='a', b='c')
for i, j in regular_dict.items():
    regular_dict[i + j] = j


# This will create an infinite loop and consume all memory
# in python3, but work in python2.
d = OrderedDict([('a', 'a'), ('b', 'b')])
for i, j in d.items():
    d[i + j] = j