Basic Syntax

No Semicolons, No Ceremony

Unlike many languages, Python does not need semicolons at the end of each line. It also does not require a main() function to run. Python scripts execute top-to-bottom, and you can start writing useful code immediately.

print("Hello")
print("World")

Indentation Is Law

In most languages, curly braces { } define blocks of code. In Python, indentation does the job. This is not optional — it is part of the language. If you indent wrong, your code breaks.

Most Python developers use 4 spaces per indentation level. Do not mix tabs and spaces.

if 5 > 2:
    print("Five is greater than two")
    print("This is inside the if block")
print("This is outside")

Variables Without Type Declarations

You do not need to declare variable types in Python. Just assign a value and Python figures out the type automatically.

name = "Alice"
age = 25
height = 5.6
is_student = True

You can check a variable's type using the type() function:

print(type(name))     # <class 'str'>
print(type(age))      # <class 'int'>
print(type(height))   # <class 'float'>
print(type(is_student)) # <class 'bool'>

Python Data Types

Python has several built-in data types you will use constantly:

String Formatting

Python has a powerful way to embed variables in strings called f-strings. Put an f before the quote and use curly braces {} to insert variables.

name = "Alice"
age = 25

# f-string (recommended)
print(f"My name is {name} and I am {age}")

# Older methods still work
print("My name is {} and I am {}".format(name, age))
print("My name is %s and I am %d" % (name, age))

Getting User Input

Use the input() function to get text from the user. It always returns a string, so you need to convert it for numbers.

name = input("What is your name? ")
print(f"Hello, {name}!")

age = int(input("How old are you? "))
print(f"In 10 years you will be {age + 10}")

Comments

Use the # symbol to write comments. Comments are ignored by Python and are only for humans reading the code.

# This is a comment
print("Comments are useful")

# You can use comments to explain tricky code
result = (42 * 7) + 3  # Why 42? It's the answer to everything

Multiple Assignments

Python lets you assign multiple variables in one line.

# Assign multiple values
x, y, z = 1, 2, 3
print(x, y, z)  # 1 2 3

# Same value to multiple variables
a = b = c = 0
print(a, b, c)  # 0 0 0

# Swap values without a temporary variable
x, y = 10, 20
x, y = y, x
print(x, y)  # 20 10