Python Core | VoidX Academy

26. Python Scope

Core Concept

Python Scope

A variable is only available from inside the region it is created. This is called scope.

Understanding scope is critical because it dictates what variables you have access to at any given line of code, and prevents variables in different parts of your program from accidentally interfering with each other.

Local Scope

A variable created inside a function belongs to the local scope of that function, and can only be used inside that function.

def myfunc():
    x = 300
    print(x)

myfunc()

Output300

Function Inside Function

The local variable can be accessed from a function within the function. The inner function has access to the outer function's scope.

def myfunc():
    x = 300
    def myinnerfunc():
        print(x)
    myinnerfunc()

myfunc()

Output300

Global Scope

A variable created in the main body of the Python code is a global variable and belongs to the global scope. Global variables are available from within any scope, global and local.

x = 300

def myfunc():
    print(x)

myfunc()
print(x)

Output300 300

Naming Variables

If you operate with the same variable name inside and outside of a function, Python will treat them as two separate variables. One available in the global scope (outside the function) and one available in the local scope (inside the function).

x = 300

def myfunc():
    x = 200
    print(x)

myfunc()
print(x)

Output200 300

The global Keyword

If you need to create a global variable, but are stuck in the local scope, you can use the global keyword. The global keyword makes the variable global.

x = 300

def myfunc():
    global x
    x = 200

myfunc()
print(x)

Output200

💡Best Practice: Overusing the global keyword can make your code very difficult to debug, as any function could unexpectedly change the variable's value. It is generally better to pass variables as arguments into your functions.

26. Python Scope

Core Concept

Python Scope

A variable is only available from inside the region it is created. This is called scope.

Local Scope

A variable created inside a function belongs to the local scope of that function, and can only be used inside that function.

def myfunc():
    x = 300
    print(x)

myfunc()

Output300

Function Inside Function

The local variable can be accessed from a function within the function. The inner function has access to the outer function's scope.

def myfunc():
    x = 300
    def myinnerfunc():
        print(x)
    myinnerfunc()

myfunc()

Output300

Global Scope

A variable created in the main body of the Python code is a global variable and belongs to the global scope. Global variables are available from within any scope, global and local.

x = 300

def myfunc():
    print(x)

myfunc()
print(x)

Output300 300

Naming Variables

x = 300

def myfunc():
    x = 200
    print(x)

myfunc()
print(x)

Output200 300

The global Keyword

If you need to create a global variable, but are stuck in the local scope, you can use the global keyword. The global keyword makes the variable global.

x = 300

def myfunc():
    global x
    x = 200

myfunc()
print(x)

Output200

26. Python Scope

Python Scope

Local Scope

Function Inside Function

Global Scope

Naming Variables

The global Keyword

Knowledge Check

26. Python Scope

Python Scope

Local Scope

Function Inside Function

Global Scope

Naming Variables

The global Keyword

Knowledge Check