Convert range(r) to list of strings of length 2 in python

Use string formatting and list comprehension:

>>> lst = range(11)
>>> ["{:02d}".format(x) for x in lst]
['00', '01', '02', '03', '04', '05', '06', '07', '08', '09', '10']

or format:

>>> [format(x, '02d') for x in lst]
['00', '01', '02', '03', '04', '05', '06', '07', '08', '09', '10']

zfill does exactly what you want and doesn't require you to understand an arcane mini-language as with the various types of string formatting. There's a place for that, but this is a simple job with a ready-made built-in tool.

ranger = [str(x).zfill(2) for x in range(r)]

Here's my take on it:

>>> map('{:02}'.format, xrange(12))
['00', '01', '02', '03', '04', '05', '06', '07', '08', '09', '10', '11']

For your own enlightenment, try reading about the format string syntax.