Can someone please help me convert this simple C ROT cipher code to Python code?

[nilamo]

The first thing you should do is define some input/outputs. Some test strings, and what you expect the rotated values to be. Does "z" become 'm' or 'M', for example. What does whitespace rotate to? Digits?

From there, the string module is probably the next best place to look.

>>> import string
>>> dir(string)
['Formatter', 'Template', '_ChainMap', '_TemplateMetaclass', '__all__', '__builtins__', '__cached__', '__doc__', '__file__', '__loader__', '__name__', '__package__', '__spec__', '_re', '_string', 'ascii_letters', 'ascii_lowercase', 'ascii_uppercase', 'capwords', 'digits', 'hexdigits', 'octdigits', 'printable', 'punctuation', 'whitespace']
>>> string.ascii_letters
'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ'