Python Password Validation: Unable to use constants from string library in regex

问题

def check_password(pw):
    global reason
    while True:
        if not re.search(string.ascii_lowercase,pw):
            flag = False
            reason = get_error(4)
            break

        elif not re.search(string.ascii_uppercase, pw):
            flag = False
            reason = get_error(1)
            break

        elif not re.search(string.digits, pw):            
            flag = False
            reason = get_error(2)
            break
        elif not re.search(string.punctuation, pw):          
            flag = False
            reason = get_error(3)
            break
        else:
            flag = True
            print("Valid Password") 
            break
        return flag

flag = False
min_length = 5

#password = input("Please enter your password:")
password = getpass.getpass("Enter Password:")

if len(password) >= min_length:
    check_password(password)
    print(password)
    if flag == True:
        print("Valid Password!")
    else:
        print(reason)
else:           
    print("Your password is not long enough.")

Here I am using regex to validate a password. I was successful if I hardcode the pattern "[A-Z]", "[0-9]", but now if I use string library constants, I am getting the message from the 1st check, irrespective of anything else wrong in the password.

Can you tell me where I am wrong, syntactically or semantically?

回答1:

The constants only contain chunks of characters, but you want to create character classes out of them. That means you need to enclose all of them with [ and ]. Also, you need to make sure some characters are escaped (^, -, ] and \), otherwise the punctuation regex will not be matching what you expect.

So, you need to replace string.ascii_lowercase with f"[{string.ascii_lowercase}]", string.ascii_uppercase with f"[{string.ascii_uppercase}]", string.digits with f"[{string.digits}]", string.punctuation with f"[{string.punctuation.replace("\\", "\\\\").replace("-", r"\-").replace("^", r"\^").replace("]", r"\]")}]".

If your Python environment is older than 3.7 and does not support string interpolation, use str.format, e.g. if not re.search(r"[{}]".format(string.ascii_lowercase),pw) and so on.

来源：https://stackoverflow.com/questions/59140483/python-password-validation-unable-to-use-constants-from-string-library-in-regex

标签

python

regex

string