Python Syntax

Python's defining syntax rule: indentation defines blocks, instead of curly braces { } like many other languages use.

if True:
    print("This line is inside the if block")
    print("So is this one")
print("This line is not — it always runs")

A line ending in : (like if True:) opens a new block; every line indented underneath it belongs to that block. The standard indent is 4 spaces.

Common mistakes

• Mixing tabs and spaces for indentation — Python will raise an error rather than guess. Configure your editor to insert spaces when you press Tab.
• Inconsistent indentation (3 spaces on one line, 4 on the next) inside the same block.