Largest distinct substring

main.py

def all_unique(s):
    d = set()
    for c in s:
        if c in d:
            return False
        else:
            d.add(c)
    return True


def find_largest_distinct_substring(s):
    n = len(s)
    while n>0:
        for i in range(len(s)-n+1):
            substring = s[i:i+n]
            if all_unique(substring):
                return substring       
        n-=1
    raise
 
print(find_largest_distinct_substring("abcbda"))
print(find_largest_distinct_substring("abca"))
print(find_largest_distinct_substring("bbbb"))
print(find_largest_distinct_substring("bbacbbc"))
print(find_largest_distinct_substring("abdefgabef"))