Ternary conditional expression in Python - Step-by-Step Execution

Concept Flow - Ternary conditional expression

Evaluate condition

Yes↓

Use value if True

↓

End

No↓

Use value if False

↓

End

The ternary expression first checks a condition. If true, it returns the first value; otherwise, it returns the second value.

Execution Sample

Python

x = 10
result = "Even" if x % 2 == 0 else "Odd"
print(result)

This code checks if x is even or odd and prints the result.

Execution Table

Step	Condition (x % 2 == 0)	Result	Value Chosen	Output
1	10 % 2 == 0	True	"Even"	"Even"
2	Print result	-	-	Even

💡 Condition evaluated once; result printed; program ends.

Variable Tracker

Variable	Start	After Step 1	After Step 2
x	10	10	10
result	undefined	"Even"	"Even"

Key Moments - 2 Insights

Why does the ternary expression only evaluate one of the two values?

Because the condition is checked first (see execution_table step 1). Only the value matching the condition's truth is chosen and evaluated.

What happens if the condition is False?

The expression chooses the value after else (not shown in this example, but see concept_flow). It skips the first value and uses the second.

Visual Quiz - 3 Questions

Look at the execution_table at step 1, what is the condition's result?

A True

B False

C 10

D Even

💡 Hint

Check the 'Condition (x % 2 == 0)' and 'Result' columns at step 1.

At which step is the variable 'result' assigned a value?

A Step 2

B Step 1

C Before Step 1

D Never

💡 Hint

Look at variable_tracker for 'result' changes after Step 1.

If x was 7 instead of 10, what would be the output?

A "Even"

B 7

C "Odd"

D Error

💡 Hint

Think about the condition x % 2 == 0 when x is 7, and check concept_flow.

Concept Snapshot

Ternary conditional expression syntax:
value_if_true if condition else value_if_false

It evaluates the condition first.
If True, returns value_if_true.
If False, returns value_if_false.
Useful for simple if-else in one line.

Full Transcript

The ternary conditional expression in Python lets you choose between two values based on a condition in a single line. First, the condition is checked. If it is true, the expression returns the first value; if false, it returns the second. For example, with x = 10, the expression "Even" if x % 2 == 0 else "Odd" checks if x is even. Since 10 % 2 == 0 is true, it returns "Even". This value is then printed. Variables change as follows: x starts at 10 and stays the same; result is assigned "Even" after the condition check. This expression only evaluates the value matching the condition's result, not both. If x were 7, the condition would be false, so the expression would return "Odd" instead.