In Python, we can attach nonlocal variables to nested functions by defining them as default arguments of the nested function. This technique is useful when we want to modify a nonlocal variable in a nested function, but we don't want to use the nonlocal keyword.
Here's an example:
def outer_function(): x = 1 def inner_function(y=x): y += 1 print(y) inner_function() print(x)outer_function() |
In this example, we define the outer_function that defines a local variable x with a value of 1. Inside the outer_function, we define the inner_function that takes a default argument y that is set to the value of x. This attaches the nonlocal variable x to the inner_function as the default value of y.
We then modify y by adding 1 to it and print the value of y from the inner_function and the value of x from the outer_function.
When we call the outer_function, it prints 2 from the inner_function and then 1 again from the outer_function.
Using default arguments to attach nonlocal variables to nested functions can be a cleaner and more readable alternative to using the nonlocal keyword. However, it should be used with caution, as it can make the code more complex if there are many nested functions or if there are many nonlocal variables involved.