Global keyword in Python - Step-by-Step Execution

Concept Flow - Global keyword

Start

↓

Define global variable

↓

Define function

↓

Inside function: use 'global' keyword

↓

Modify global variable

↓

Function ends

↓

Global variable changed outside function

↓

End

This flow shows how a global variable is defined, then modified inside a function using the 'global' keyword, affecting the variable outside the function.

Execution Sample

Python

x = 5

def change():
    global x
    x = 10

change()
print(x)

This code changes a global variable x inside a function using the global keyword and prints the updated value.

Execution Table

Step	Action	Variable 'x' Value	Output
1	Initialize x = 5	5
2	Define function change()	5
3	Call change()	5
4	Inside change(): declare global x	5
5	Inside change(): assign x = 10	10
6	change() ends	10
7	print(x)	10	10

💡 Program ends after printing updated global variable x = 10

Variable Tracker

Variable	Start	After change() call	Final
x	5	10	10

Key Moments - 2 Insights

Why do we need the 'global' keyword inside the function?

Without 'global', assigning to x inside the function creates a new local variable x, not changing the global one. See step 4 and 5 in execution_table where 'global x' allows modifying the global x.

What happens if we remove the 'global' keyword and assign x = 10 inside the function?

The global x remains 5 because the assignment creates a local x inside the function. The print outside still shows 5. This is explained by the difference in step 5 if 'global' was missing.

Visual Quiz - 3 Questions

Look at the execution_table, what is the value of x right after step 5?

A 5

B 10

C Undefined

D 0

💡 Hint

Check the 'Variable x Value' column at step 5 in the execution_table.

At which step does the global variable x actually change its value?

A Step 2

B Step 4

C Step 5

D Step 7

💡 Hint

Look for the assignment to x inside the function in the execution_table.

If we remove the 'global' keyword, what will be printed at step 7?

A 5

B 10

C Error

D None

💡 Hint

Refer to the key_moments section explaining the effect of removing 'global'.

Concept Snapshot

Global keyword in Python:
- Use 'global var' inside a function to modify a global variable.
- Without 'global', assignment creates a local variable.
- Changes to global variables affect code outside the function.
- Syntax:
  global x
  x = new_value

Full Transcript

This visual execution shows how the global keyword works in Python. First, a global variable x is set to 5. Then a function change() is defined, which uses 'global x' to tell Python that x inside the function is the global one. Inside change(), x is set to 10. When change() is called, it updates the global x to 10. Finally, printing x shows 10, confirming the global variable was changed. Without the global keyword, the assignment inside the function would create a local x, leaving the global x unchanged at 5. This is a common beginner confusion. The execution table tracks each step and variable value, helping learners see exactly when and how the global variable changes.