Summary: Functions in Python


Keywords: functions, input parameters, top-down programming

Functions Python programming

A function in Python is a block of operations performed when the function is called. The function can take input parameters and use these to make calculations. Functions can also return values when the function is executed.

What is a function in Python?

A function is a block of operations that are performed when called. This means that instead of rewriting the same code several times, we can instead reuse code that is run multiple times, in different places in the program. A function can get one or more values, so-called input parameters, and can also send back, return one or no value. By return is meant what the method “returns” when it has performed the operations it contains. A method is always terminated when a value has been returned.

Function Python Programming

Syntax: Declare a function in Python

When creating a function, you need to specify the input parameters, and whether the function will return any values. We can design our function in several ways:

def function_name(input parameter):
    “Function Documentation”
    what the function should perform
    return value

When should I use a function in Python?

  • Reusable code: If you need to do the same thing (or almost the same thing) many times over, write a function to do it, and then use that function every time you perform that task. 
  • Top-down programming: A beneficial approach in programming is called top-down programming. You solve a big problem, which is seen as the “top”, by breaking it down into smaller problems. 
  • Visualize the problem: Use function to break down the task in your mental picture of the problem, making it much easier for you to work with your programs if you break them down and try to visualize them in smaller parts. 
  • Simplify: Sometimes, we do not need to know how a function works; we are only interested in what it does. This means that, as mentioned earlier, we can focus on the main problem and focus on what our function produce, rather than how they do it.

Why use functions in Python?

This chapter has looked at the basics to create a function. A function is a block of operations that is independent of the other code. This way we can call the function at any time and thus build up large programs of several small functions. The functions are therefore like small building blocks that together create large programs.