Return values in Python - Step-by-Step Execution

Concept Flow - Return values

Function called

↓

Execute function code

↓

Return value reached?

No→Continue executing

Yes↓

Send value back to caller

↓

Function ends

When a function is called, it runs its code until it hits a return statement, then sends back a value and stops.

Execution Sample

Python

def add(a, b):
    return a + b

result = add(3, 4)
print(result)

This code defines a function that adds two numbers and returns the sum, then prints the result.

Execution Table

Step	Action	Evaluation	Result
1	Call add(3, 4)	Parameters a=3, b=4	Function starts
2	Calculate a + b	3 + 4	7
3	Return 7	Return value reached	7 sent back to caller
4	Assign result = 7	Store returned value	result = 7
5	Print result	Print 7	Output: 7

💡 Function ends after return statement sends value back

Variable Tracker

Variable	Start	After Step 3	After Step 4	Final
a	undefined	3	undefined	undefined
b	undefined	4	undefined	undefined
result	undefined	undefined	7	7

Key Moments - 3 Insights

Why does the function stop running after the return statement?

Because the return statement sends a value back and immediately ends the function, as shown in step 3 of the execution_table.

What happens if there is code after the return statement?

That code does not run because the function already ended at the return, as seen in the execution flow where return ends the function.

How does the returned value get used outside the function?

The returned value is assigned to a variable (result) outside the function, shown in step 4 where result gets the value 7.

Visual Quiz - 3 Questions

Look at the execution_table, what is the value of 'result' after step 4?

A undefined

B 7

C 3

D None

💡 Hint

Check the 'result' variable in variable_tracker after step 4

At which step does the function send the value back to the caller?

A Step 3

B Step 2

C Step 4

D Step 5

💡 Hint

Look for the step where 'Return value reached' happens in execution_table

If the return statement was removed, what would happen to the output?

A Output would be 7

B Output would be an error

C Output would be None

D Output would be 0

💡 Hint

Without return, function returns None by default, so result would be None

Concept Snapshot

def function_name(params):
    return value

- 'return' sends a value back to where the function was called
- Function stops running after return
- Returned value can be stored or used outside
- If no return, function returns None by default

Full Transcript

When you call a function, it runs its code. When it reaches a return statement, it sends a value back to the caller and stops running. This returned value can be saved in a variable or used directly. If the function has no return statement, it returns None automatically. For example, a function that adds two numbers returns their sum with return a + b. The program then can print or use that sum. The return statement is important because it ends the function and gives back a result.