Functions

A function is a named block of code you can run again and again.

Define and call

python
def my_function():
    print("Hello from a function")

my_function()

### Hello from a function

def defines it; the name followed by () calls it.

Arguments

Pass values in parentheses:

python
def greet(name):
    print("Hello " + name)

greet("Ada")

### Hello Ada

Parameters vs arguments

• Parameter: the variable in the definition (name).
• Argument: the value you pass when calling ("Ada").

Number of arguments must match

python
def full(fname, lname):
    print(fname + " " + lname)

full("Emil", "Refsnes")

### ok
full("Emil")

### TypeError: missing argument

Return a value

return sends a result back:

python
def add(a, b):
    return a + b

print(add(5, 3))

### 8

pass as a placeholder

python
def empty():
    pass

TL;DR

• def name(): defines; name() calls.
• Arguments go in parentheses; counts must match.
• return gives back a value.
• A function without return gives None.