How is variable lookup performed in different scopes in Python?

In Python, variable lookup follows the LEGB rule, which indicates the scope in the following order:

• L (Local) — the local scope of a function or method.
• E (Enclosing) — the scope of enclosing (outer) functions.
• G (Global) — the global scope of the current module.
• B (Built-in) — Python's built-in names.

When the interpreter encounters a variable name, it first searches in the local scope, if not found — it moves to enclosing functions, then to the global scope, and finally to built-in names. If the variable is not found anywhere, a NameError occurs.

Example:

x = 'global'

def outer():
    x = 'enclosing'
    def inner():
        x = 'local'
        print(x)  # Will print 'local'
    inner()
    print(x)      # Will print 'enclosing'

outer()
print(x)          # Will print 'global'