Indentation

Python uses indentation, not braces, to group code into blocks.

Syntaxif condition: do_something()

Most languages group code with curly braces. Python uses indentation — the spaces at the start of a line — instead. This forces clean, readable code.

The rules

  • A block starts after a line ending in a colon :.
  • Every line in the same block must be indented by the same amount.
  • The standard is 4 spaces per level.

Getting indentation wrong is one of the most common beginner errors, so be consistent.

Example

Example · python
temperature = 30
if temperature > 25:
    print('It is warm')
    print('Wear light clothes')
print('Done')

# Output:
# It is warm
# Wear light clothes
# Done

When to use it

  • A developer structures an if/else block so only the correct branch runs based on user input.
  • A Python linter flags mixed tabs and spaces, causing an IndentationError that breaks the build.
  • A nested loop processes rows and columns of a spreadsheet using two levels of indentation.

More examples

If block with indentation

Shows that the two indented lines are inside the if block; the last line always runs.

Example · python
temperature = 30
if temperature > 25:
    print('It is warm')
    print('Wear light clothes')
print('Have a good day')

# Output:
# It is warm
# Wear light clothes
# Have a good day

Nested indentation levels

Demonstrates two levels of indentation for nested loops, each adding 4 spaces.

Example · python
for row in [1, 2]:
    for col in ['A', 'B']:
        cell = f'{col}{row}'
        print(cell)

# Output:
# A1
# B1
# A2
# B2

IndentationError example

Illustrates that missing indentation after a colon causes an IndentationError.

Example · python
# This code has a wrong indentation and will raise IndentationError:
# if True:
# print('oops')  # no indent — error!

# Correct version:
if True:
    print('correct')

# Output:
# correct

Related

py syntaxpy if else

Discussion

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