Indentation

Python · Reference cheat sheet

📋 Overview

Python uses indentation (leading spaces) to define code blocks instead of braces \{\}. Consistent indentation is required syntax. The community standard is 4 spaces per level (PEP 8).

🔧 Core concepts

Empty blocks need pass. Mixing tabs and spaces in one file causes TabError or confusing bugs.

💡 Examples

if / else blocks:

score = 85

if score >= 90:
    print("A")
elif score >= 80:
    print("B")
else:
    print("keep practicing")

Nested indentation:

for n in range(1, 4):
    print(f"n={n}")
    if n % 2 == 0:
        print("  even")
    else:
        print("  odd")
print("done")  # back at top level

Functions and pass:

def todo_later():
    pass  # placeholder body


def add(a, b):
    total = a + b
    return total

Wrong vs right (conceptually):

# Wrong — body not indented (IndentationError)
# if True:
# print("hi")

# Right
if True:
    print("hi")

⚠️ Pitfalls

• Mixing tabs and spaces — configure the editor to insert spaces.
• Copy-pasting from the web can bring inconsistent indent widths.
• Only indent when a block is required; random indent is a syntax error.
• IndentationError / TabError messages point near the problem line — check the line above too.

🔗 Related

• getting_started.md
• comments.md
• boolean_logic.md
• conditionals (if present in your notes set)