Global scope in Python - Step-by-Step Execution

Concept Flow - Global scope

Start Program

↓

Define global variable

↓

Define function

↓

Call function

↓

Inside function: Access global variable

↓

Function ends

↓

Program ends

The program starts by defining a global variable, then a function that uses it. When the function is called, it accesses the global variable from the global scope.

Execution Sample

Python

x = 10

def print_x():
    print(x)

print_x()

This code defines a global variable x and a function that prints x, then calls the function.

Execution Table

Step	Action	Variable 'x' Value	Output
1	Define global variable x = 10	10
2	Define function print_x()	10
3	Call print_x()	10
4	Inside print_x(), print(x)	10	10
5	Function print_x() ends	10
6	Program ends	10

💡 Program ends after function call and output printed

Variable Tracker

Variable	Start	After Step 1	After Step 3	Final
x	undefined	10	10	10

Key Moments - 2 Insights

Why does the function print_x() print the value of x even though x is not defined inside it?

Because x is defined in the global scope before the function is called, the function can access it. See execution_table step 4 where print(x) outputs 10.

What if we try to change x inside the function without declaring it global?

Without declaring x as global inside the function, Python treats it as a new local variable. This can cause errors or unexpected behavior. This example only reads x, so no problem occurs.

Visual Quiz - 3 Questions

Look at the execution_table at step 4, what value does print_x() print?

A 0

B 10

C undefined

D Error

💡 Hint

Check the 'Output' column at step 4 in execution_table.

At which step is the global variable x first defined?

A Step 1

B Step 2

C Step 3

D Step 4

💡 Hint

Look at the 'Action' column in execution_table for when x is assigned.

If we added 'x = 5' inside print_x() without 'global' keyword, what would happen?

A The global x changes to 5

B An error occurs immediately

C A new local x is created inside print_x()

D The function prints 10

💡 Hint

Recall that assigning to a variable inside a function creates a local variable unless declared global.

Concept Snapshot

Global scope means variables defined outside functions.
Functions can read global variables directly.
To modify global variables inside functions, use 'global' keyword.
Without 'global', assignments create local variables.
Global variables exist throughout program execution.

Full Transcript

This example shows a global variable x set to 10. A function print_x() prints x. When called, print_x() accesses the global x and prints 10. The variable tracker shows x stays 10 throughout. Key points: functions can read global variables without declaring them. But to change them, you must declare 'global x' inside the function. The quiz checks understanding of when x is defined, what print_x() outputs, and what happens if you assign x inside the function without 'global'.