python3.5变化（String）

2.7代码实现查询字符串内字符的数量

import string

def letterCount(str):
    count = 0
    for s in str:
        if s.lower()  in string.lowercase:
            print()
            count += 1
    return count
question = "What is your name?"
print(letterCount(question))

但我用的是3.5，string.lowercase 找不到，查找后发现是做了改变。代码如下：

import string

def letterCount(str):
    count = 0
    for s in str:
        if s.lower() in string.ascii_lowercase:
            print()
            count += 1
    return count
question = "What is your name?"
print(letterCount(question))