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Programming Using Pre Existing Libraries Edexcel

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Programming Using Pre-Existing Libraries

What is a pre-existing library?

A pre-existing library is reusable code that can be used throughout a program
The code has been made public through reusable modules or functions
Using pre-existing libraries saves programmers time by using working code that has already been tested
Some examples of pre-existing libraries are:
- Random
- Math
- Turtle

Programming Random Library

What is the random library?

The random library is a library of code which allows users to make use of ‘random‘ in their programs
Examples of random that are most common are:
- Random choices
- Random numbers
Random number generation is a programming concept that involves a computer generating a random number to be used within a program to add an element of unpredictability
Examples of where this concept could be used include:
- Simulating the roll of a dice
- Selecting a random question (from a numbered list)
- National lottery
- Cryptography

Concept	Python
Random numbers	`import random` `number = random.randint(1,10)` `number = random.randint(-1.0,10.0)`
Random choice	`import random` `choice = random.choice()`

Concept

Python

Random numbers

import random

number = random.randint(1,10)

number = random.randint(-1.0,10.0)

Random choice

import random

choice = random.choice()

Examples in Python

Random code
# importing random library `import random` # asking user to enter a username and password `user = input("Enter a username: ")` `pw = input("Enter a password: ")` # checking if the user and password are correct `if user == "admin" and pw == "1234":` # generating a random 4 digit code `code = random.randint(1000,9999)` `print("Your code is", code)`

Random code

# importing random library

import random

# asking user to enter a username and password

user = input("Enter a username: ")
pw = input("Enter a password: ")

# checking if the user and password are correct

if user == "admin" and pw == "1234":

# generating a random 4 digit code
code = random.randint(1000,9999)

print("Your code is", code)

National lottery
`import random` # Create a list of numbers for the national lottery `lottery_numbers = list(range(1, 50))` # Create an empty list to store the chosen numbers `chosen_numbers = []` # Loop to pick 6 numbers from the list `for _ in range(6):` # Use random.choice to pick a number from the list `number = random.choice(lottery_numbers)` # Add the chosen number to the list of chosen numbers `chosen_numbers.append(number)` # Remove the chosen number from the list of available numbers `lottery_numbers.remove(number)` # Sort the chosen numbers in ascending order `chosen_numbers.sort()` # Output the chosen numbers `print("The winning numbers are:", chosen_numbers)`

National lottery

import random

# Create a list of numbers for the national lottery

lottery_numbers = list(range(1, 50))

# Create an empty list to store the chosen numbers

chosen_numbers = []

# Loop to pick 6 numbers from the list

for _ in range(6):

# Use random.choice to pick a number from the list

number = random.choice(lottery_numbers)

# Add the chosen number to the list of chosen numbers

chosen_numbers.append(number)

# Remove the chosen number from the list of available numbers

lottery_numbers.remove(number)

# Sort the chosen numbers in ascending order

chosen_numbers.sort()

# Output the chosen numbers

print("The winning numbers are:", chosen_numbers)

Programming Math Library

What is the math library?

The math library is a library of code which allows users to make use of mathematical operations which can be performed with ease
Examples of math that are most common are:
- math.pi – the constant Pi $straight pi$
- math.sqrt (x) – returns the square root of a number
- math.floor(x) – returns the largest number, not less than x
- math.ceil (x) – returns the smallest number, not less than x

Concept	Python	Output
Math.pi	`import math` `radius = 7` `circleArea = (radius*2) math.pi`	153.94
Math.sqrt(x)	`import random` `number = 200` `print(math.sqrt(number)`	14.14
Math.floor(x)	`print(math.floor(32.7))`	32
Math.ceil(x)	`print(math.ceil(32.7))`	33

Programming Turtle Library

What is the turtle library?

The turtle library is a pre-built library of code which allows the creation of images and shapes using a ‘pen’
Examples of turtle that are most common include:
- Polygons
- Complex shapes such as spirographs
The turtle library uses a canvas which is based on X, Y coordinates
Turtle includes a series of simple instructions which can be used along with fundamental programming constructs to create drawings
It is important to note that just like all libraries, the user must import turtle at the beginning of the program

Concept	What it does	Python Example
turtle.pendown()	Puts the pen down ready to begin drawing	`turtle.pendown()`
turtle.penup()	Lifts the pen up to stop drawing if moving the pen	`turtle.penup()`
turtle.forward(x)	Moves the turtle forward the number steps in the brackets	`turtle.pendown()`
turtle.right(x)	Turns the turtle right to the number of degrees specified	`turtle.right(90)`
turtle.left(x)	Turns the turtle left to the number of degrees specified	`turtle.left(90)`
turtle.setpos(x,y)	Moves the turtle to the position declared	`turtle.setpos(0, 30)`

Computer Science GCES EDEXCEL

Programming Using Pre Existing Libraries Edexcel

Programming Using Pre-Existing Libraries

What is a pre-existing library?

Programming Random Library

What is the random library?

Examples in Python

Programming Math Library

What is the math library?

Programming Turtle Library

What is the turtle library?

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