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Python Language Conditional Expression (or "The Ternary Operator")


The ternary operator is used for inline conditional expressions. It is best used in simple, concise operations that are easily read.

  • The order of the arguments is different from many other languages (such as C, Ruby, Java, etc.), which may lead to bugs when people unfamiliar with Python's "surprising" behaviour use it (they may reverse the order).
  • Some find it "unwieldy", since it goes contrary to the normal flow of thought (thinking of the condition first and then the effects).
n = 5

"Greater than 2" if n > 2 else "Smaller than or equal to 2"
# Out: 'Greater than 2'

The result of this expression will be as it is read in English - if the conditional expression is True, then it will evaluate to the expression on the left side, otherwise, the right side.

Tenary operations can also be nested, as here:

n = 5
"Hello" if n > 10 else "Goodbye" if n > 5 else "Good day"

They also provide a method of including conditionals in lambda functions.