Lesson 2: Conditionals and Loops

Day 3

Programming Basics

This lesson will go over how to loop over data and use conditionals to add dynamic code to your project. This lesson will assume you have a working Python environment using Python (3.10.12) or later.

Conditional

To check if a variable is equal to a value, use the if statement

age = 5
if (age == 5):
   print("You are 5 years old")

Output:

You are 5 years old

Note that we used two equal signs. This notes that it is a condition, not a declaration of a variable. Code that runs after a condition is true must be indented either 2 or 4 spaces relative to the statement

To use the greater, greater or equal, less, less or equal signs, use the following signs in order > (greater), >= (greater or equal), < (less), (<=) less or equal

age = 4
if (age < 5):
   print("You are less than 5 years old")

Output:

You are less than 5 years old

The same is true for all the other signs

Negation

To run the statement if the condition is NOT True use the exclamation mark ! or use the not keyword

name = "Bob"
if (name != "John"):
   print("Your name is Bob")

This piece of code run if the name is NOT "John"

Else statements

This piece of code runs if the previous condition is not true. For example if the age is not greater than 15 than can run another condition

name = "Bob"
if (name != "John") # Name is NOT John
  print("Your name is not John")
else: ## Name is John
  print("Your name is John")

The else statement will run ONLY if the name is John

Else if statements

This piece of code runs if the previous condition is not true. Unlike an else this includes a condition. Multiple elif statements can be used in parallel going from the top to the bottom

name = "Bob"
if (name == "Bob")
  print("Your name is Bob")
else if (name == "John"):
   print("Your name is John")
else if (name == "Edward"):
  print("Your name is Edward")
else:
  print("Your name is not Bob John or edward")

Output

Your name is Bob

The code will run top to bottom from the if to the else. If the condition isn't met it will go to the next statement.

Day 4

Loops

Loops make it easier to run a piece of code continuously until a condition is fulfilled. There are 2 main types of loops: a while loop and a for loop

While Loops

While loops run until a condition is fulfilled. If that condition is not fulfilled it will continue running. If you put while (True) it will run forever, while doing While(False) will make it not run

password = ""
while (password != "password123")
  password = input("Please enter the password ")
print("Access Granted")

Input

Please enter the password bob
Please enter the password bob2
Please enter the password password123

Output

Access Granted

For Loops

For loops run for a set number of times, not until a condition is fulfilled. For example you can make it run 3 times then exit.

for i in range(5):
  print(i)

Output

0
1
2
3
4

In this loop i represents the current number and range(5) represents the number up to 5, but not including 5 (0, 1, 2, 3, 4)

Break statements

Break statements manually exit the loop even if the outer condition is not fulfilled or the set number of times the loop should run is not reached

for i in range(5):
  print(i)
  if (i == 2):
    break

Output

0
1
2

Next Steps

Read the next lesson (1.3)