Searching for digits

So I figured out how to do the process with the re module, however prior to that I was trying to do it without any import. I was able to match upper and lower case letters, but I could not find a built in function to detect numbers. Any ideas?

def check(x): capital = 0 lower = 0 digit = 0

if len(x) > 9:
    for c in x:
        if c == c.upper():
            capital += 1
        elif c == c.lower():
            lower += 1
        elif c == c.digit():
            digit += 1
elif capital >= 1 and lower >= 1 and digit >= 1:
    return True or False

check(x)