Goals

• Distinguish and apply different data types
• Formulate simple conditions with if-else
• Use comparison operators correctly

Data Types of Variables

In the last block, you learned how to work with variables, meaning you can now initialize variables, assign values to them, and calculate with them. According to the container model, variables seem to always hold numbers. In reality, variables we define can hold values of very different types, meaning values other than just numbers.

Data Type Name	What Python Expects	Example in Python
Integer (int)	whole number	x = 3, number = -5
Float (float)	decimal number	height = 163.5, speed = 4.52
String (str)	text	name = "Thomas", msg = "Hello World"
Boolean (bool)	truth value (true/false)	win = True, lost = False

The good news: Python often handles management automatically. If we want to calculate with integers and decimal numbers at the same time, that's no problem at all.

import turtle
t = turtle.Turtle()

i = 10
f = 3.6
t.write(i - f) 

However, if you try to simply calculate with a string of letters, it won't work.

import turtle
t = turtle.Turtle()

text = "Hello"
t.write(10 + text)

:::detail Explanation This results in an error because Python doesn't know how to add a number and text together. :::

Simple Conditionals

Simple Conditions

You already know conditions from Karol. Sometimes you had to check with IsWall whether Karol was standing in front of a wall and decide based on this condition whether she should take a step forward. Conditions are therefore crucial for the flow of your program and become particularly interesting when we can design them ourselves with variables.

import turtle
t = turtle.Turtle()

x = 6
if x < 5:
    t.write("x is less than 5!")
else:
    t.write("x is greater than or equal to 5!")

:::detail Explanation Tobi first checks if the condition x < 5 is True. It's not, so he doesn't execute the instruction t.write("x is less than 5!"). Since there's an else, he executes the alternative. :::

Note the often forgotten colon after the condition.

Possible Comparison Operators

Operator	Name	Example Condition	Value for x that gives True	Value for x that gives False
==	Equality	x == 5	5	3
!=	Inequality	x != 5	3	5
<	Less than	x < 5	4	5
<=	Less than or equal	x <= 5	5	6
>	Greater than	x > 5	6	5
>=	Greater than or equal	x >= 5	5	4

Warning

One of the most common programming mistakes is confusing = and ==. We know = as the assignment operator from variables. With x == 5 we check whether this condition is true.

Tasks

Task 1: Age Groups

Write a program that stores a person's age in a variable and outputs an appropriate message based on age:

• Under 12: "You are a child"
• 12-17: "You are a teenager"
• 18 and over: "You are an adult"

Task 2: Grade Output

Create a program that converts a point score (0-15) into a grade:

• 15-13 points: "Excellent"
• 12-10 points: "Good"
• 9-7 points: "Satisfactory"
• 6-4 points: "Sufficient"
• Under 4 points: "Insufficient"

Task 3: Temperature Check

Write a program that evaluates a temperature:

• Under 0°C: "It's freezing"
• 0-10°C: "It's cold"
• 11-25°C: "Pleasant temperature"
• Over 25°C: "It's warm"

Preparation for Block 3

Prepare for linked conditions by thinking about how you could check multiple conditions simultaneously.