Verifying patterns of various filenames

Question

I have a large number of images that were named in a odd way and because of that, when they're displayed in a file browser, they're completely out of order. However, since they weren't named in a completely random manner, I can use regex to properly rename them, once I understand all the subpatterns that went into it. So far I only understood two.

So I'm going to create a program to verify the pattern of each filename, make a set out of it with a sample of each name, and then try to understand the patterns and subpatterns.

def get_pattern(name):
    pattern = []
    for letter in name:
        if letter.isalpha():
            pattern.append('a')
        elif letter.isdigit():
            pattern.append('0')
        else:
            pattern.append(letter)
    return ''.join(pattern)

It's pretty straightforward to loop through the images and then check the pattern for each image.

My questions:

1. Is there a way to make the code more concise? Maybe using a dictionary?
2. Is there something in re or other easily available library that does this? Is using isalpha() and isdigit() the way to go here?

Answer 1

This will make your example work in the same way you intended to.

patterns = []
patterns.append(lambda x: 'A' if x.isalpha() else x)
patterns.append(lambda x: '0' if x.isdigit() else x)

def get_pattern(name):
    for pattern in patterns:
        name = map(pattern, name)
    return ''.join(name)

Additionally you can register new patterns. Here is an example:

>>> get_pattern('Mario Cesar 2013')
'AAAAA AAAAA 0000'

About your objective, if you want just to sanitize the file names, will be the best to use a different approach, look at https://github.com/ksze/sanitize

Answer 2

This is more compact, but not necessarily better:

def get_pattern(name):
    return ''.join([(c.isalpha() and 'a') or (c.isdigit() and '0') or c for c in name])

The parentheses are optional.

Answer 3

You could use map:

def get_pattern(name):
    def simplify(character):
        if character.isalpha():
            return 'a'
        elif character.isdigit():
            return '0'
        return character
    return ''.join(map(simplify, name))

... or translate:

import string
translation = string.maketrans(string.ascii_letters + string.digits,
                               'a' * len(string.ascii_letters) +
                               '0' * len(string.digits))
def get_pattern(name):
    return name.translate(translation)