string merges

from random import choice, randint
from string import ascii_lowercase


def create_strs(num=5, low=3, high=6):
    "return list of two-string tuples with <num> elements"
    "strings formed as per the new_str function"

    def new_str():
        "return string consisting of a lower case letter repeated"
        "a random number of times (between <low> and <high>)"
        return choice(ascii_lowercase) * randint(low, high)

    return [(new_str(), new_str()) for _ in range(randint(5, 10))]


def balance(alpha, beta):
    "return string of whichever is longer of <alpha> or <beta>"
    "that constitutes the substring of the longer part"
    "(return empty string if same length)"
    len_alpha = len(alpha)
    len_beta = len(beta)
    if len_alpha < len_beta:
        return beta[len_alpha:]
    elif len_beta < len_alpha:
        return alpha[len_beta:]
    else:
        return ""


source = create_strs(20)  # list of 20 tuples of random strings
for first, second in source:
    merged = "".join(
        [letter for letter_pair in zip(first, second) for letter in letter_pair]
    ) + balance(first, second)
    print(f"{merged:12} {len(merged):2}: {len(first)} + {len(second)}")