Variables
name = "Ali"
age = 16
print(name, age)No type keyword is needed. Python works out the type from the value.
Indentation and colons
Python uses indentation (usually 4 spaces) instead of curly brackets to group code. Lines that start a block — if, for, while, def, class — end with a colon.
if age >= 18:
print("Adult")
else:
print("Student")Comments, print() and input()
# This is a comment — Python ignores it
city = input("Your city: ")
print("Hello from", city)input() always returns text. Use int(input()) to get a number.
Common syntax errors
SyntaxError: a missing colon, bracket or quote.IndentationError: lines in a block are not lined up.NameError: a misspelled variable name (Python is case-sensitive).
Practice exercises
Try each one yourself first, then open it in the Visualizer to watch every line run.
Exercise 1
Introduce yourself
Store your name and age in variables, then print one sentence using both.
name = "Ali"
age = 15
# print: Ali is 15 years old
Hint
Use commas inside print() to join a text and a number.
Show solution and explanation
name = "Ali"
age = 15
print(name, "is", age, "years old")Each variable is a labelled box in memory. print() puts spaces between the items separated by commas, so no + or str() is needed.
Watch the solution step by stepExercise 2
Fix the indentation
This program has an indentation error. Fix it so it prints both lines.
score = 8
if score > 5:
print("Good job")
print("Finished")Hint
Lines that belong to the if must be pushed in by 4 spaces.
Show solution and explanation
score = 8
if score > 5:
print("Good job")
print("Finished")The colon starts a block, and the indented lines form that block. "Finished" is not indented, so it runs whether the condition is true or false.
Watch the solution step by stepExercise 3
Update a variable
Start with coins = 10, add 5, then double it and print the result.
coins = 10
# add 5, then double
print(coins)Hint
Write coins = coins + 5 and then coins = coins * 2.
Show solution and explanation
coins = 10
coins = coins + 5
coins = coins * 2
print(coins) # 30Python works out the right side first using the old value, then stores the result back in the same box. Watch coins change 10 → 15 → 30.
Watch the solution step by step