Python Cyber Security - Check and print valid passwords from a file

Last update on April 24 2025 12:42:22 (UTC/GMT +8 hours)

5. Password File Validator

Write a Python program that reads a file containing a list of passwords, one per line. It checks each password to see if it meets certain requirements (e.g. at least 8 characters, contains both uppercase and lowercase letters, and at least one number and one special character). Passwords that satisfy the requirements should be printed by the program.

password.txt:

Pas1$Ku1
password
password123
password123$
Password6#(%
Germany#12
USA12^$#
England0#

Sample Solution:

Python Code:

import re
def check_password(password):
    # Define regular expressions for each requirement
    length_regex = re.compile(r'^.{8,}$')
    uppercase_regex = re.compile(r'[A-Z]')
    lowercase_regex = re.compile(r'[a-z]')
    digit_regex = re.compile(r'\d')
    special_regex = re.compile(r'[\W_]')
    
    # Check if password meets each requirement
    length_check = length_regex.search(password)
    uppercase_check = uppercase_regex.search(password)
    lowercase_check = lowercase_regex.search(password)
    digit_check = digit_regex.search(password)
    special_check = special_regex.search(password)
    
    # Return True if all requirements are met, False otherwise
    if length_check and uppercase_check and lowercase_check and digit_check and special_check:
        return True
    else:
        return False

# Open file containing passwords
with open('passwords.txt') as f:
    # Read each password from file and check if it meets requirements
    for password in f:
        password = password.strip()  # Remove newline character
        if check_password(password):
            print("Valid Password: "+password)
        else:
            print("Invalid Password: "+password)

Sample Output:

Valid Password: Pas1$Ku1
Invalid Password: password
Invalid Password: password123
Invalid Password: password123$
Valid Password: Password6#(%
Valid Password: Germany#12
Invalid Password: USA12^$#
Valid Password: England0#

Flowchart:

For more Practice: Solve these Related Problems:

Write a Python program to read a file containing one password per line, validate each password against set criteria, and print only those that pass.
Write a Python function that reads a text file of passwords, checks each for length and complexity, and returns a list of valid passwords.
Write a Python script to process a password file, outputting a summary report with counts of valid and invalid passwords.
Write a Python program to read a file of passwords, validate them, and then write the valid ones to a new file while logging the invalid ones.

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Python Code Editor:

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