Week 2

Python Basics - Conditional Logic and Input

Spyder setup

1. Start by creating a new folder somewhere on your computer called "python_classes" and then create another folder inside called "week2" - This is where you'll be placing the python scripts (.py files) which you write today

2. Open up Spyder and create a new file inside the week2 folder called "hello_world.py"

3. Add a print statement which outputs hello world to the console, and make sure that it runs by pressing the green arrow in the toolbar and checking for the print output in the console

Login system

This week we're going to create a simple login system by using the input() function, and if statements.

Storing user information

For the time being, we're going to store user information in separate variables. Let's start by adding a user with the following details:

Name: Alex Password: 1234

In order to check the name and password in two separate steps, you'll have to store this information in two separate variables

Checking the username

Using the input() function, ask users to enter their username, then check that the value they entered exactly matches the one in the database (e.g. "Alex") - use print statements to let the user know if they entered an incorrect username

Checking the password

Now use input() again when the user has entered the correct username, but this time ask for the password. If the user succeeds in typing in a correct username-password pair, you should print a secret message.

Extension 1 - Case sensitivity

Using the .lower() function (see extension material), make the username check non-caps sensitive.

1. Try and use the function only once, by reassigning the input immediately after gathering it

2. Make sure that your database only contains lowercase usernames - otherwise some people will never be able to login

Extension 2 - Two users

Using the logical and/or operations, add the ability for another user (with a distinct username-password pair) to login

You'll need to make use of nested if-statements to ensure the password matches the username

We'll see a far more elegant way of adding more users to our database in subsequent weeks (using dictionaries!).

Extension 3 - Bad Passwords

Warning

Using the in operation (see extension material), have a go at users who have passwords containing the substrings "1234" or "pass" or "word", but only once they've logged in successfully

Password Change

Instead of just berating the user for their poor choice of password, give them the option to change their password (i.e. override the old one).

Once they've changed their password, print it out to confirm it worked.