How to make a password generator with python.

In this tutorial we will make a password generator with the secrets module. Why not random module? see the first post in this series to understand.

So Let's Begin!

Problem

Generate a random password, according to the user input.

Sub problems

Get user input
Create lists for letters etc...
Loop over lists and make a password.
Print the password.

Let's write some code!

Get user input Here we will use try/except blocks so that when user types a string we do not get an error.

We will get inputs for number of special characters, small letters, big letters and numbers required for generating the password.

Code:

try:
        num_of_numbers = int(input("How many numbers should your password have: "))
except ValueError:
        num_of_numbers = int(input("How many numbers should your password have: "))
try:
        num_of_special = int(
        input("How many special characters should your password have: "))
except ValueError:
        num_of_special = int(
        input("How many special characters should your password have: "))
try:
        num_of_small_letters = int(
        input("How many small letters should your password have: "))
except ValueError:
        num_of_small_letters = int(
        input("How many small letters should your password have: "))
try:
        num_of_cap_letters = int(
        input("How many big letters should your password have:  "))
except ValueError:
        num_of_cap_letters = int(
        input("How many big letters should your password have:  "))

### Create Lists for numbers to choose from.

We could hardcode this like:

number_list = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

But this will take us way more time!
So let's use the string module!

import string
number_list = list(string.digits)

But we could just have a string right? then why make it list you will find this out later on in this blog!

Let's do this for everything.

import string

smallLetters = list(string.ascii_lowercase)

bigLetters = list(string.ascii_uppercase)

specialCharacters = list(string.punctuation)

numbers = list(string.digits)

So now we can loop over these lists, and make a list!

First let's declare empty variables!

spPart = ""

numPart = ""

smallPart = ""

bigPart = ""

Now let's loop over the lists.

for i in range(1, num_of_numbers + 1):
        randNum = secrets.choice(numbers)
        numPart = numPart + str(randNum)


    for i in range(1, num_of_special + 1):
        randSp = secrets.choice(specialCharacters)
        spPart = spPart + randSp


    for i in range(1, num_of_small_letters + 1):
        randSm = secrets.choice(smallLetters)
        smallPart = smallPart + randSm


    for i in range(1, num_of_cap_letters + 1):
        randBig = secrets.choice(bigLetters)
        bigPart = bigPart + randBig

Now let's add the parts to make a password.

password = numPart + spPart + smallPart + bigPart

Now let's refactor the code, by putting this into a function.

def generate_password( num_of_numbers, num_of_special, num_of_small_letters, num_of_cap_letters):

    smallLetters = list(string.ascii_lowercase)

    bigLetters = list(string.ascii_uppercase)

    specialCharacters = list(string.punctuation)

    numbers = list(string.digits)

    spPart = ""

    numPart = ""

    smallPart = ""

    bigPart = ""

    # ANCHOR: Generating Password
    for i in range(1, num_of_numbers + 1):
        randNum = secrets.choice(numbers)
        numPart = numPart + str(randNum)


    for i in range(1, num_of_special + 1):
        randSp = secrets.choice(specialCharacters)
        spPart = spPart + randSp


    for i in range(1, num_of_small_letters + 1):
        randSm = secrets.choice(smallLetters)
        smallPart = smallPart + randSm


    for i in range(1, num_of_cap_letters + 1):
        randBig = secrets.choice(bigLetters)
        bigPart = bigPart + randBig

    password = numPart + spPart + smallPart + bigPart

    return password