Learn Functional Programming in Python/

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What Is a Closure?

What Is a Closure?

Get ready to be introduced to closures and learn about the need and benefits of using closures.

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In functional programming, we sometimes write functions that create other functions. A simple and elegant way to do this is to use a closure. Closures provide a way to create functions dynamically, a little like lambdas but far more powerful.

Inner functions

Let’s start by looking at inner functions. An inner function is a function that is defined inside another function. Here is an example:

Python 3.8
def print3(): 
  def print_hello(): 
      print('hello') 
  print_hello() 
  print_hello() 
  print_hello() 
# Main code 
print3() 
print_hello() # This will give an error

print_hello is an inner function of print3. Specifically, print3 first defines print_hello, then calls it three times.

The result when we run the main code is:

  • Calling print3 prints “hello” three times.
  • Calling print_hello gives an error because it is only visible from inside print3.

Returning an inner function

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