Python program to check the validity of a Password (original) (raw)

Last Updated : 06 Sep, 2024

In this program, we will be taking a password as a combination of alphanumeric characters along with special characters, and checking whether the password is valid or not with the help of a few conditions.

Primary conditions for password validation:

1. Minimum 8 characters.
2. The alphabet must be between [a-z]
3. At least one alphabet should be of Upper Case [A-Z]
4. At least 1 number or digit between [0-9].
5. At least 1 character from [ _ or @ or $ ].

**Examples:

Input : R@m@_f0rtu9e$
Output : Valid Password

Input : Rama_fortune$
Output : Invalid Password
Explanation: Number is missing

Input : Rama#fortu9e
Output : Invalid Password
Explanation: Must consist from _ or @ or $

**Way 1:

Here we have used the **re module that provides support for regular expressions in Python. Along with this the re.search() method returns False (if the first parameter is not found in the second parameter) This method is best suited for testing a regular expression more than extracting data. We have used the re.search() to check the validation of alphabets, digits, or special characters. To check for white spaces we use the “\s” which comes in the module of the regular expression.

Python `

Python program to check validation of password

Module of regular expression is used with search()

import re password = "R@m@f0rtu9e$" flag = 0 while True: if (len(password)<=8): flag = -1 break elif not re.search("[a-z]", password): flag = -1 break elif not re.search("[A-Z]", password): flag = -1 break elif not re.search("[0-9]", password): flag = -1 break elif not re.search("[@$]" , password): flag = -1 break elif re.search("\s" , password): flag = -1 break else: flag = 0 print("Valid Password") break

if flag == -1: print("Not a Valid Password ")

`

**Time complexity: O(n), where n is the length of the password string.
**Auxiliary space: O(1), as we are using only a few variables to store intermediate results.

**Way 2:

Python `

l, u, p, d = 0, 0, 0, 0 s = "R@m@_f0rtu9e$" if (len(s) >= 8): for i in s:

    # counting lowercase alphabets 
    if (i.islower()):
        l+=1            

    # counting uppercase alphabets
    if (i.isupper()):
        u+=1            

    # counting digits
    if (i.isdigit()):
        d+=1            

    # counting the mentioned special characters
    if(i=='@'or i=='$' or i=='_'):
        p+=1           

if (l>=1 and u>=1 and p>=1 and d>=1 and l+p+u+d==len(s)): print("Valid Password") else: print("Invalid Password")

`

**Time complexity: O(n) where n is the length of the input string s.
**Auxiliary space: O(1) as it only uses a few variables to store the count of various characters.

**Way 3: Without using any built-in method

Python `

l, u, p, d = 0, 0, 0, 0 s = "R@m@f0rtu9e$" capitalalphabets="ABCDEFGHIJKLMNOPQRSTUVWXYZ" smallalphabets="abcdefghijklmnopqrstuvwxyz" specialchar="$@" digits="0123456789" if (len(s) >= 8): for i in s:

    # counting lowercase alphabets
    if (i in smallalphabets):
        l+=1            

    # counting uppercase alphabets
    if (i in capitalalphabets):
        u+=1            

    # counting digits
    if (i in digits):
        d+=1            

    # counting the mentioned special characters
    if(i in specialchar):
        p+=1        

if (l>=1 and u>=1 and p>=1 and d>=1 and l+p+u+d==len(s)): print("Valid Password") else: print("Invalid Password")

`

**Time complexity : O(n), where n is the length of the input string s.
**Auxiliary space : O(1), as here only few variables are used to store the intermediate results.