Password validation in Python
Let's take a password as a combination of alphanumeric characters along with special characters, and check whether the password is valid or not with the help of few conditions. Conditions for a valid password are:
- Should have at least one number.
- Should have at least one uppercase and one lowercase character.
- Should have at least one special symbol.
- Should be between 6 to 20 characters long.
Input : Geek12# Output : Password is valid. Input : asd123 Output : Invalid Password !!
We can check if a given string is eligible to be a password or not using multiple ways. Method #1: Naive Method (Without using Regex).
# Password validation in Python
# using naive method
# Function to validate the password
def password_check(passwd):
SpecialSym =['$', '@', '#', '%']
val = True
if len(passwd) < 6:
print('length should be at least 6')
val = False
if len(passwd) > 20:
print('length should be not be greater than 8')
val = False
if not any(char.isdigit() for char in passwd):
print('Password should have at least one numeral')
val = False
if not any(char.isupper() for char in passwd):
print('Password should have at least one uppercase letter')
val = False
if not any(char.islower() for char in passwd):
print('Password should have at least one lowercase letter')
val = False
if not any(char in SpecialSym for char in passwd):
print('Password should have at least one of the symbols $@#')
val = False
if val:
return val
# Main method
def main():
passwd = 'Geek12@'
if (password_check(passwd)):
print("Password is valid")
else:
print("Invalid Password !!")
# Driver Code
if __name__ == '__main__':
main()
Password is valid
This code used boolean functions to check if all the conditions were satisfied or not. We see that though the complexity of the code is basic, the length is considerable. Method #2: Using regex compile() method of Regex module makes a Regex object, making it possible to execute regex functions onto the pat variable. Then we check if the pattern defined by pat is followed by the input string passwd. If so, the search method returns true, which would allow the password to be valid.
# importing re library
import re
def main():
passwd = 'Geek12@'
reg = "^(?=.*[a-z])(?=.*[A-Z])(?=.*\d)(?=.*[@$!%*#?&])[A-Za-z\d@$!#%*?&]{6,20}$"
# compiling regex
pat = re.compile(reg)
# searching regex
mat = re.search(pat, passwd)
# validating conditions
if mat:
print("Password is valid.")
else:
print("Password invalid !!")
# Driver Code
if __name__ == '__main__':
main()
Password is valid.
Using ascii values and for loop:
This code uses a function that checks if a given password satisfies certain conditions. It uses a single for loop to iterate through the characters in the password string, and checks if the password contains at least one digit, one uppercase letter, one lowercase letter, and one special symbol from a predefined list and based on ascii values. It sets a boolean variable "val" to True if all these conditions are satisfied, and returns "val" at the end of the function.
The time complexity of this code is O(n), where n is the length of the password string. The space complexity is O(1), as the size of the variables used in the function does not depend on the size of the input.
def password_check(passwd):
SpecialSym =['$', '@', '#', '%']
val = True
if len(passwd) < 6:
print('length should be at least 6')
val = False
if len(passwd) > 20:
print('length should be not be greater than 8')
val = False
# Check if password contains at least one digit, uppercase letter, lowercase letter, and special symbol
has_digit = False
has_upper = False
has_lower = False
has_sym = False
for char in passwd:
if ord(char) >= 48 and ord(char) <= 57:
has_digit = True
elif ord(char) >= 65 and ord(char) <= 90:
has_upper = True
elif ord(char) >= 97 and ord(char) <= 122:
has_lower = True
elif char in SpecialSym:
has_sym = True
if not has_digit:
print('Password should have at least one numeral')
val = False
if not has_upper:
print('Password should have at least one uppercase letter')
val = False
if not has_lower:
print('Password should have at least one lowercase letter')
val = False
if not has_sym:
print('Password should have at least one of the symbols $@#')
val = False
return val
print(password_check('Geek12@')) # should return True
print(password_check('asd123')) # should return False
print(password_check('HELLOworld')) # should return False
print(password_check('helloWORLD123@')) # should return True
print(password_check('HelloWORLD123')) # should return False
#This code is contributed by Edula Vinay Kumar Reddy
Output
True Password should have at least one uppercase letter Password should have at least one of the symbols $@# False Password should have at least one numeral Password should have at least one of the symbols $@# False True Password should have at least one of the symbols $@# False
