Functions are an essential part of programming, as they can execute a block of code at once. Often it's an excellent way to re-use blocks of code.
Let's give it a go and see how they work in Python.
Creating a function in Python
A function is made by prefixing the def keyword.
def foo():
print("Bar")
However, running our code now will not do anything since we didn't call our function yet.
Executing the function
To run/execute the function, we must call it somewhere in our code. In general, this happens when a specific criterion is matched, but let's just run it as is.
def foo():
print("Bar")
foo()
When we run our code now, it returns Bar
Passing and returning data
Having a function that prints out something is not convenient so let's see how we can give it data and return something.
Let's say we want to make a function that multiplies a number by itself and returns the output.
Meaning, if we put in the number 5, it should run 5x5 and return 25.
def multiply(number):
return number * number
print(multiply(5))
Running this code will indeed return 25.
We can easily have the function accept multiple arguments like so:
def multiply(number, multiplier):
return number * multiplier
print(multiply(5, 10))
This will return 50.
And one cool thing we can do is send the arguments based on their key value like this.
multiply(number=5, multiplier=2)
You might not know how many arguments you're expecting in some cases, and you can prepend the argument with an asterisk (*).
def feed_animals(*animals):
print(animals)
print(animals[1])
feed_animals('Cow', 'Chicken', 'Goat')
Which will return:
('Cow', 'Chicken', 'Goat')
Goat
There are some more additions to functions, but this covers the basics for Python functions.
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