# Functions in Python—easy or hard to learn & master?
This week I'll be looking at aspects of functions which can be tricky for those who know basics and want to move to next level. If you've learnt about functions in Python are keen to take the next step, then hopefully this series of toots will help…
Let's start with the unexciting but important—terms
• _define_
• _call_
• _parameter_
• _argument_
Here's the code we'll use as an example which you can also get from the ALT text of the image in this toot:
`def greet_person(person):`
`print(f"Hello {person}! How are you doing today?")`
`greet_person("Ishaan")`
`greet_person("Elizabeth")`
You can follow this thread in the replies (unlisted)
/1
#Python #functions #coding #programming #LearnToCode #LearnPython
# — Define —
You _define_ the function when you use the `def` keyword
The first line of the definition is the function signature and the code after the colon is the code you want the function to perform…
However, this code does not run when you define a function
For this, we need to call the function…
/2
# — Call —
You _call_ a function when you use it
You're calling a function when you write its name followed by parenthesis (the round brackets)…
The code in the function definition will run when you call a function
In the example above, you're calling the function twice on the last two lines of the code
/3
# — Parameter —
A _parameter_ is the name you choose for information that's needed by the function
You add parameters inside the brackets in the function signature which is the line which includes `def`
In this example, the parameter is `person`
This is the name of the "storage box" which is ready to hold any information you send into the function
However, when you define the function, this "box" is still empty…
/4
# — Argument —
An _argument_ is the actual information you send to a function when you call it
You called the function twice in the example above
The first time you called `greet_person()` you used the argument `"Ishaan"` and the second time `"Elizabeth"`
When you call the function, the information (the argument) is stored in a variable named `person` inside the function
Don't worry too much if you confuse parameters and arguments. Many programmers confuse them, too!
/5
"What's in a name?", one might argue? And there's a point. What matters most is knowing how to use concepts rather than knowing the precise definitions
Still, these terms are used everywhere-in documentation, in tutorials, when talking to other programmers
So, knowing the terminology _is_ important. It shouldn't be the first thing someone learns, but eventually, everyone should become familiar with the right terms for the right things
/6
Later this week, I'll look at other aspects relating to #Python #functions that can confuse those beginners moving on to more intermediate levels, including:
• _positional and named arguments_
• _optional arguments_ (by defining default values)
• the "obscure" _args and kwargs_
• forcing _positional-only_ or _keyword-only_ arguments using the "rogue" forward slash `/` and asterisk `*` in the function signature
• _type-hinting_ when defining functions
• some best practices when defining and using functions
Some of these topics I've written about a while ago in this Real Python article: https://realpython.com/python-optional-arguments/
