Why scope matters in Python - Visual Breakdown

Concept Flow - Why scope matters

Start program

↓

Define variable x = 5

↓

Enter function

↓

Check if function uses global or local x

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Uses local x

↓

Local x created

↓

Function ends

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Print x outside function

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End program

This flow shows how variables inside and outside functions can be different because of scope, affecting which variable is used or changed.

Execution Sample

Python

x = 5

def func():
    x = 10
    print(x)

func()
print(x)

This code shows a variable x outside and inside a function, printing both to see how scope affects their values.

Execution Table

Step	Action	Variable x value	Output
1	Assign x = 5 globally	5
2	Define function func()	5
3	Call func()	5
4	Inside func(), assign local x = 10	10 (local)
5	Inside func(), print local x	10 (local)	10
6	func() ends, local x discarded	5 (global)
7	Print global x	5	5

💡 Program ends after printing global x; local x inside func() does not affect global x.

Variable Tracker

Variable	Start	After func() call	Final
x (global)	5	5	5
x (local in func)	N/A	10	N/A

Key Moments - 3 Insights

Why does the print inside the function show 10 but the print outside shows 5?

Inside the function, x is a new local variable set to 10 (see step 4 and 5 in execution_table). Outside, the global x remains 5 (step 7). They are different variables because of scope.

Does changing x inside the function change the global x?

No, because the x inside the function is local and separate from the global x. The global x stays unchanged (see variable_tracker and steps 6 and 7).

What happens to the local x after the function ends?

The local x is discarded after the function finishes (step 6). It only exists during the function call.

Visual Quiz - 3 Questions

Look at the execution_table, what is the value of x inside the function at step 4?

A 5

B 10

C Undefined

D None

💡 Hint

Check the 'Variable x value' column at step 4 in the execution_table.

At which step does the program print the global x value?

A Step 5

B Step 3

C Step 7

D Step 1

💡 Hint

Look for the step where output is '5' in the execution_table.

If the function did not assign x locally, what would the print inside func() show?

A 5

B 10

C Error

D Nothing

💡 Hint

Think about what variable x the function would use if no local assignment exists, referencing variable_tracker.

Concept Snapshot

Scope means where a variable exists and can be used.
Variables inside functions are local by default.
Local variables do not change global variables with the same name.
Changing a local variable does not affect the global one.
Understanding scope helps avoid bugs and confusion.

Full Transcript

This lesson shows why scope matters in Python. We start by assigning x = 5 globally. Then we define a function func() that assigns x = 10 locally and prints it. When we call func(), it prints 10 because it uses the local x. After func() ends, the local x disappears. Printing x outside the function shows 5, the global x unchanged. This shows local and global variables with the same name are different because of scope. Changing local x does not affect global x. Understanding this helps avoid mistakes when working with variables inside and outside functions.