Python Nested Functions

In this blog, we will understand the python concept of nested functions, and use that concept to build a function for mathematical raise power!

Let's dive in!

Introduction

Let's say that we want to use a process a number of times within a function.

For example, we want a function that takes 3 numbers as parameters

and performs the same function on each of them.

One way would be to write out the computation 3 times

However, this definitely does not scale if you need to perform the computation many times!

What we can do instead is define an inner function within our function definition, such as we will do next, and call it where necessary. This is called a nested function.

The syntax for the inner function is exactly the same as that for any other function!

Looks Better! Right?

Raise to Power Function

Let's now look at another important usage of Nested Functions in creating a function that returns a function without calling it!

So each time we call the outer function it creates for us a new inner one!

I know it's hard to understand this way, so let's see our raise_val(n) function.

In this example, we define an outer function raise_val, which contains an inner function called inner.

Now look at what raise_val returns:

It returns the inner function inner !

raise_val takes an argument n and creates a function inner that returns the nth power of any number.

That's a bit complicated and will be clearer when we use the function raise_val

Things will get clearer now!

Passing the number 2 to raise_val creates a function that squares any number.

Similarly, passing the number 3 to raise_val creates a function that cubes any number ! Isn't that amazing!

One interesting detail:

When we call the function square, it remembers the value n=2, although the enclosing scope defined by raise_val and to which n=2 is local, has finished execution! This is a subtlety referred to as a closure in Computer Science and it shouldn't concern you too much. And that is why it is also called enclosing function.

Well, that is all. Congrats in understanding one of the coolest things python provides!

The code and the explanation are available on my GitHub. Have fun with python!