Count number of occurrences of a specific digit with order keeping

counter.py

from collections import Counter


def convert(value):
    value = str(value)
    cnt = Counter(value)

    res = []
    for el in cnt:
        res.append(el)
        res.append(str(cnt.get(el)))

    return int("".join(res))


def equals(actual, expected):
    if actual == expected:
        return True
    else:
        print("Expected: '{}', but was '{}'".format(expected, actual))
        return False


assert equals(convert(1234), 11213141)
assert equals(convert(11213141), 15213141)
assert equals(convert(1121231234), 14233241)