python判断是否含有下划线

如何检测字符串中的下划线，还有如果又有大写又有小写又该怎么判断（大写不是首位的情况）

password = input()

level = []
for l in password:
    if l.isupper():
        level.append('up')
    if l.islower():
        level.append('low')
    if l == '_':
        level.append('_')
    if l.isdigit():
        level.append('int')
print(len(set(level)))

from string import *

def check_in_pwd(chars):
    return any([s in password for s in chars])

password = input()
safety = 0

if len(password) > 6: #检查长度
    for chars in [ascii_lowercase,
                  ascii_uppercase,
                  digits,
                  "_"]:
        if check_in_pwd(chars):
            safety += 1

    print(safety)