0510---字符串练习题

import string
def isalpha(s):
    for i in s:
        if i in string.ascii_letters:
            continue
        else:
            return False
    return True

print(isalpha("abc"))
print(isalpha("abc1"))

def isdigit(s):
    for i in s:
        if i in "0123456789":
            continue
        else:
            return False
    return True

print(isdigit("123"))
print(isdigit("1a2b3c"))

def isalnum(s):
    for i in s:
        if (i>=‘a‘ and i<=‘z‘) or (i>=‘A‘ and i<=‘Z‘) or (i in "0123456789"):
            continue
        else:
            return False
    return True

print(isalnum("ha h1"))
print(isalnum("a234vb"))

def join(s1,s2=None):
    result =""
    if s2==None:
        s2=""
    for i in s1:
        result +=i+s2

    return result

print(join(("r", "u", "n", "o", "o", "b"),"-"))