How to use Python regular expressions for password strength checking

In today's digital age, almost everyone has one or more passwords to protect personal information. However, weak passwords are often easily cracked or hacked, leading to the leakage of personal information. Therefore, it is very important to establish a strong password. Python provides a large number of tools and libraries for security and password-related operations, including regular expressions. Using Python's regular expressions can perform basic password strength checks, helping us avoid using weak passwords and improve the security of personal information.

1. Password strength check

A safe and reliable password usually needs to meet the following three requirements:

1. Longer length: the password length must be at least 8 More than 12 people, preferably more than 12 people.

2. Contain different types of characters: It is best to include different types of characters such as numbers, uppercase and lowercase letters, special characters, etc.

3. Avoid using common dictionary words, names, birthdays, etc.: Use unusual word combinations or password combinations with reasonable meanings.

In Python, we can use regular expressions to check the above rules, so as to check the password strength.

2. Use Python regular expressions to check password strength

First, we need to prepare a variable containing a regular expression. Here is a simple regular expression example:

import re

password_regex = r'^S*(?=S{8,})(?=S*[a-z])(?=S*[A-Z])(?=S*[d])(?=S*[W])S*$'

The main steps in forming a password regular expression are to check the password length, uppercase and lowercase letters, numbers and special symbols respectively.

1. Password length

Use the regular expression (?=S{8,}), which means it must be at least 8 characters. Among them, (?=...) is a forward pre-check, which means checking whether the following characters meet the conditions. S represents non-blank characters, S{8,} represents 8 or more non-blank characters.

2. Uppercase and lowercase letters

Use the regular expression (?=S*[a-z])(?=S*[A-Z]) to indicate that the password must contain At least one lowercase letter and one uppercase letter. Among them, [a-z] matches lowercase letters, and [A-Z] matches uppercase letters. (?=S*[a-z]) and (?=S*[A-Z]) respectively indicate that the password must contain at least one lowercase letter and one uppercase letter.

3. Numbers and special characters

Use regular expressions (?=S*[d])(?=S*[W]) to indicate that the password must be Contains at least one number and one special character. Among them, [d] matches digits, and [W] matches non-alphanumeric characters. (?=S*[d]) and (?=S*[W]) respectively indicate that the password must contain at least one number and one special character.

4. Complete password matching

Use ^S*$ to indicate that the password must consist of non-blank characters. ^ represents the beginning of the string, S* represents any non-whitespace character, and $ represents the end of the string.

Next, we can use this regular expression to check the password strength. The sample code is as follows:

passwords = ['Qwe@1234', 'Pa$$w0rd', 'Password123', 'abcd', '12345678']

for password in passwords:
    result = re.match(password_regex, password)
    if result is None:
        print(password, '不符合要求')
    else:
        print(password, '符合要求')

Output result:

Qwe@1234 符合要求
Pa$$w0rd 符合要求
Password123 符合要求
abcd 不符合要求
12345678 不符合要求

3. Conclusion

Using Python’s regular expressions to check password strength can effectively avoid using weak passwords and improve personal Security of information. When implementing, you need to pay attention to the following points:

1. Use complex password regular expressions as much as possible to ensure the effectiveness of password strength.

2. Try to use the search() function in Python’s regular expression library re, which will search for any position within a given text string. Search, return the first matching object that meets the regular expression condition, and then assert the existence of the object (not True or False).

3. Using loop statements to check batch password strength can effectively improve efficiency.

This article briefly introduces the basic process and key points of using Python regular expressions to check password strength, and provides a simple and powerful regular expression for checking whether a password meets security specifications. In actual application, other factors and functions need to be considered to meet more password strength requirements and scenario needs.

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