Conditionals

if runs a block only when its condition is true. elif ("else if") checks another condition if the first was false, and else catches everything else.

Example: a time-of-day greeting

hour = 14

if hour < 12:
    greeting = "Good morning"
elif hour < 18:
    greeting = "Good afternoon"
else:
    greeting = "Good evening"

print(greeting)

Good afternoon

Python uses indentation, not curly braces, to mark which lines belong to which block. This isn't optional style here the way it is in many languages: inconsistent indentation is an actual syntax error in Python, not just something a linter complains about. That constraint is deliberate, it makes it structurally impossible to write Python code where the indentation lies about what the code actually does.