Python: Local, Nonlocal and Global variables

Rahul S
2 min readSep 27, 2023
  • nolocal is used when we need to access a variable in a nested function.global makes a previously declared variable global.

‘nonlocal` and `global` keywords are used to specify the scope of variables within functions and classes. They are used to indicate whether a variable should be treated as a local variable, a nonlocal variable, or a global variable. Here’s what each of these keywords is used for:

1. `local` variables: Variables defined within a function/method are local to that function/method. They can only be accessed within the scope of the function or method in which they are defined.

2. `nonlocal` variables: The `nonlocal` keyword is used within a nested function. It is not local to the nested function but belongs to the nearest enclosing function that is not a global function. We can modify a variable in an outer (enclosing) function’s scope from within an inner function.

def outer_function():
x = 10

def inner_function():
nonlocal x
x = 20

inner_function()
print(x)

# This will print 20
```

3. `global` variables: Variables defined outside any function or at the global scope are global. They can be accessed and modified from any part of the code, including within functions.

If we need to modify a global variable from within a function, we use the `global` keyword. It refers to the global variable and does not create a local variable.

x = 10
def modify_global():
global x
x = 20

modify_global()
print(x)

# This will print 20

In summary,

  • `nonlocal` is used to modifies variables in an enclosing (non-global) function’s scope from within a nested function, while
  • `global` is used to access and modify global variables from within functions.

These keywords help control variable scope and prevent unintended variable shadowing or reassignment.

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