Indentation
Python uses indentation, not braces, to group code into blocks.
Syntax
if 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
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Press Run to execute the code.
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.
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 dayNested indentation levels
Demonstrates two levels of indentation for nested loops, each adding 4 spaces.
for row in [1, 2]:
for col in ['A', 'B']:
cell = f'{col}{row}'
print(cell)
# Output:
# A1
# B1
# A2
# B2IndentationError example
Illustrates that missing indentation after a colon causes an IndentationError.
# 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
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