check_duplicate

Write a function in Python to check duplicate letters. It must accept a string, i.e., a sentence. The function should return True and the letters repeated if the sentence has any word with duplicate letters, else return False. 

Possible inputs/outputs: 'mississippi': 'True, i, s, p' , 'hello': 'l', 'bonjour': 'o', 'twinkle': 'False'

if anyone has a different solution or a slightly altered version, please comment!

Scroll down to view my solution...

_____________________

def check_duplicate(a: str):
    global i, j
    x = sorted(list(a))
    duplicate = []
    j = 'no'
    for i in range(len(x) - 1):
        if x[i] == x[i + 1]:
            i += 1
            j = 'yes'
        elif j == 'yes':
            duplicate.append(x[i])
            j = 'no'
    if j == 'yes':
        duplicate.append(x[i])
    if not duplicate:
        return False
    else:
        return True, duplicate