How does lexical scoping work in Python?

Can you explain what lexical scoping is in Python?

Sure! Lexical scoping refers to the visibility of variables in nested functions. In Python, a function can access variables from its own scope, the enclosing scope, and the global scope.

Can you give me an example of lexical scoping in action?

Absolutely! Here's a simple example:

x = 10

def outer_function():
    y = 5
    def inner_function():
        return x + y
    return inner_function()

result = outer_function()
print(result)  # This will print 15

In this case, inner_function can access both x from the global scope and y from the enclosing outer_function.

What happens if I try to access a variable that is not in scope?

If you try to access a variable that is not in scope, Python will raise a NameError. For example, if inner_function tried to access a variable defined only in inner_function, it wouldn't be able to find it if it was not defined.

Are there any exceptions to lexical scoping in Python?

In Python, the main exception is the use of the global and nonlocal keywords. global allows you to modify a variable in the global scope, while nonlocal lets you modify a variable in the nearest enclosing scope.