Python Functions Explained with Simple Examples
Originally published on CodingCush . A Python function is a reusable block of code that does one job, runs only when you call it, and can take inputs and return a result. You define a function once with the def keyword, give it a clear name, and then use it as many times as you like — with different inputs each time. Functions are how programmers stop repeating themselves: instead of copying the…
Python functions are reusable blocks of code that perform a specific task, are called when needed, and can accept inputs and return a result. They are defined using the `def` keyword, given a clear name, and can be called multiple times with different inputs. Functions help prevent code repetition, making scripts more organized and easier to understand.
You have already used built-in functions like `print()`, `len()`, and `input()` without writing them. Now, you'll create your own functions. A function starts with `def`, followed by its name, a pair of brackets for parameters, and a colon. The code for the function is indented under the definition line. Defining a function does not execute it; it simply teaches Python the function's name and steps.
Functions can take inputs, called parameters when defined and arguments when passed during a call. These inputs act like variables within the function, receiving values from the caller. Functions can have multiple parameters, separated by commas, and can also have default values for common cases. If a function doesn't have a return statement, it returns `None`, indicating "nothing here."
Variables defined inside a function are local and only exist within that function's scope. They disappear when the function call ends. Variables defined outside the function, at the top level of the file, are global and can be accessed inside functions. This separation prevents functions from interfering with each other and with the rest of the program.
Functions can return values, which can be stored, combined, or passed to other functions. Functions that perform calculations should usually return their result, allowing the caller to use the returned value as needed. When a function reaches a `return` statement, it stops executing immediately and sends the value back to the caller. Any code after a `return` inside the same function will not be executed.
To reinforce the concepts, consider a practice function that takes a list of numbers and returns their sum. This example incorporates defining a function with parameters, using return statements, and handling local scope.
Written by urgent.news from Dev.to's reporting — not their text. Machine-written — may contain errors; check the original before relying on it.
