Functions

Functions

Functions are special blocks of code that can take input and give output

There are two important concepts to remember about functions:

• How to define them
• How to call/invoke them

# Function definition
def square(x):
  return x * x

# Function invocation
print square(3)

# OR
input = 3
input_squared = square(input)
print input_squared

When invoked, they are evaluated to expressions
They can have zero to many inputs, and an optional output

In python, indentation is very important
A function definition lasts as long as you keep the line indented
Other languages, like C/C++ or Java, use curly braces '{}' to denote when functions start and end

int square(int x) {
    return x * x;
}

Functions can have multiple parameters.

def multiply(x, y):
    z = x * y
    return z

print multiply(3, 5) # Prints 15

Functions can be invoked inside other functions
They can also have expressions as arguments

def square(x):
    return multiply(x, x)

print square(multiply(2, 3)) # Prints 36