[programming techniques] subroutines

[ BBC Bitesize 'Computational thinking, algorithms and programming ⇢ Programming techniques page 6-7 ]

Program

Sequences of instructions for a computer.

Subroutines

A small program that is written within a main program to carry out a specific function.

Code for Defining a Subroutine:

def subroutineName(parameterOne, parameterTwo)

Types of Subroutines:

• procedures

• functions

Procedures

A section of computer code that performs a specific task by taking in parameters.

Functions

A section of computer code that performs a specific task and returns a value by taking in parameters.

Benefits of Subroutines:

• usually small in size → easier to write, test, debug and understand

• can be saved separately as modules and used again in other programs → this saves time

• used repeatedly at various points → the code only has to be written once, resulting in shorter programs

Built-in Functions:

• int - converts strings or floats into integers

• str - converts a number into a string

• asc - finds the ASCII number of a character

Libraries

A collection of pre-written, tested functions that extend the functionality of a language. stored in a separate file.

Function Example:

def add(a, b)

result = a + b

return result

sum = add(5, 3)

print(sum)

Local Variables

Variables that are defined within a subroutine and can only be used in said subroutine.

Global Variables

Variables that are defined outside a subroutine but are valid both in and out of subroutines.

Parameters

Variables listed inside the parentheses when defining a subroutine. They act as placeholders for the values that will be passed to the subroutine when it is called.

Arguments

The actual values passed to the subroutine when it is called. They provide the subroutine with the data it needs to operate on.

Code for Random Number Generator (Integer):

import random

randomNumber = random.randint(1,100)

print(randomNumber)

Code for Random Number Generator (Float):

import random

#generates a random float between 0 and 1 (inclusive)

randomFloat = random.uniform(0, 1)

print(randomFloat)

Code for Random Number Generator (Arrays):

import random

items = [1, 2, 3, 4, 5]

#generates a random item from list

randomItem = random.choice(items)

print(randomItem)