Stacks and Queues using Python

Posted on March 10, 2018 by Administrator Posted in Algorithms, Computer Science, OOP Concepts, Python - Advanced, Python Challenges

Stacks and Queues are two key data structures often used in programming.

A queue is a FIFO data structure: First-In First-Out in other words, it is used to implement a first come first served approach. An item that is added (enqueue) at the end of a queue will be the last one to be accessed (dequeue).

A stack is a FILO data structure: First-In Last-Out. Imagine a stack of books piled up on a table. When you add (push) a book on top of the pile, it will be the first book that you will then take (pop) from the pile (stack).

Both stacks and queues can easily be implemented in Python using a list and the append(), pop() and remove() functions.

In the following trinket we are creating our own classes, Queue and Stack. Using Object Oriented Programming (OOP) enables us to prevent direct access to the list (defined as a private attribute – This is an example of encapsulation a key concept in OOP). It also enables us to create and name our own methods, pop(), push(), enqueue() and dequeue() to match the terminology used when using stacks or queues.

Your Task…

Update the above Stack Class and Queue Class to have an extra private property called maxCapacity (positive integer value). This property should be initialised based on a parameter passed using the constructor of each class.

The code to push a value to the Stack or enqueue a value to the queue should be amended to only push or enqueue the value if the stack or the queue have not reached their maximum capacity.

Client-Server Technologies in a Web-Based Application

Posted on March 8, 2018 by Administrator Posted in A Level Concepts, Computer Science, Computing Concepts

If you are learning to build websites you will most likely have started learning about HTML, eventually CSS and JavaScript. These three languages are client-side languages which run on your computer through the web-browser.

A website that only relies on client-side languages is called a static website. This means that the webpages remain the same unless you edit the HTML code. To start with (back in the 90s), the World Wide Web was only made of static websites.

Web 2.0

Progressively, the internet evolved to more dynamic websites. We call this web2.0.

Websites such as amazon, eBay, Facebook, etc. are dynamic websites. Their content changes constantly based on the user interactions with the site.

Web2.0 websites are full web applications that use both client-side technologies (HTML, CSS, JavaScript) and server-side technologies such as PHP, ASP, .Net, C#, Python, etc. as well as a database to store and retrieve information from (MySQL, Oracle, SQL Server).

Server-side scripts interact with the database using SQL queries to select, update, insert or delete data. They then combine this data with HTML tags to create HTML, CSS and JavaScript code that is then sent to the client computer to be viewed in the web-browser as a static web page would be viewed.

The following diagram summarises some of the key concepts of client-server web-based applications:

Relational Databases

Posted on March 8, 2018 by Administrator Posted in A Level Concepts, Computer Science, Computing Concepts, Database Concepts

Tables, Records & Fields

A table is a collection of records. Each record is made of fields.

Each field has a data type such as String/Text, Integer, Float/Real, Boolean, Date & Time, etc.

A table is a collection of records. Each record is made of fields.

Primary Keys, Foreign Keys & Relationships

The primary key is a unique identifier for each record.
e.g. the candidate number field is a primary key in the student table.

When a primary key is used to link records between two tables, it becomes a foreign key in the linked table.

There are 3 types of relationships to link tables:

One-to-One Relationships,
One-to-Many Relationships,
Many-to-Many Relationships.

Entity Relationship Diagram (ERD)

En Entity Relationship Diagram is used to represent all the entities/tables with their attributes/fields and the relationships between these entities.

SQL Language

SQL stands for Structured Query Language. SQL is a standard language used to query a relational database. SQL can be used to:

SELECT records from one or more tables
INSERT new records into a table
UPDATE records from a table
DELETE records from a table

The basic syntax of the SQL language is as follows:

SQL can also be used to change the structure of a database e.g. creating, editing or dropping tables and indexes.

Learn how to define your own SQL queries

To recap…

fields

integer

table

records

primary

Boolean

data type

foreign

linked table

identifier

A is a collection of .
Each record is made of

Each field has a such as string/text, , real/float, , date & time, etc.

The key is a unique for each record.

e.g. the candidate number field is a primary key in the student table.

When a primary key is used to link records between two tables, it becomes a key in the .

Tagged with: Database, SQL

Flowchart to Python Code – Star Rating Validation

Posted on March 6, 2018 by Administrator Posted in Computer Science, Python - Beginner, Python Challenges, Solved Challenges

The aim of this Python challenge is to validate a user input using a range check.

In this program, the user will be asked to enter a star rating by entering a number value between 0 and 5. This could for instance be used to rate a movie (5 Stars = Excellent , 0 Star = Disappointing).

The program will check that the end-user has entered a number between 0 and 5 and if not, it will display an error message and repeat the question until a valid rating between 0 and 5 is entered.

Here is the flowchart for our algorithm:

Python Code

You can now complete the Python code to implement this algorithm.

This algorithm is a good example of:

Testing

Now that your code is complete, it is important to test it to see if it is working as expected.

When testing a program, you can use different types of test and test data:

Valid Tests: To check that the program is working fine with acceptable data.
Extreme Tests: To test how your program works when you enter data that is at the limit (lower boundaries, upper boundaries) of what is considered acceptable data.
Erroneous Tests: To try to break the pogram, enter data that is not acceptable, that should be rejected and/or generate an error message.

Test #	Type of Test	Input Values	Expected Output	Actual Output
#1	Valid	Star Rating: 2	Thank You
#2	Valid Extreme	Star Rating: 0	Thank You
#3	Valid Extreme	Star Rating: 5	Thank You
#4	Erroneous	Star Rating: 9	Invalid Star Rating – Try Again Enter a star rating between 0 and 5:
#5	Erroneous	Star Rating: -2	Invalid Star Rating – Try Again Enter a star rating between 0 and 5:
#6	Erroneous	Star Rating: xyz	Invalid Star Rating – Try Again Enter a star rating between 0 and 5:

Extension Task

Did you all your test pass? If not, this means your code could be further improved.

Check this blog post to see if it could help you improve your code further and ensure all tests pass.

Adding validation routines when capturing user inputs is always a good approach to improve your programs and make them more robust.

You can investigate other forms of validation routines on this page.

Solution...

The solution for this challenge is available to full members!
Find out how to become a member:
➤ Members' Area

Tagged with: Flowchart

Flowchart to Python Code – Poker Dice Game

Posted on March 6, 2018 by Administrator Posted in Computer Science, Python - Beginner, Python Challenges, Solved Challenges

The aim of this challenge is to create a simplified game of Poker Dice using only three dice.
The computer will generate three random numbers between 1 and 6.

The program will then check to see if the three dice have the same value (“Three of a kind!”) or if any two of the three dice have the same value (“Pair”).

The game will be implemented using the following algorithm:

Python Code

Use the above flowchart to help you write the Python code to solve this challenge.

This algorithm is a good example of:

Extension Task

Could you improve your code further to find out if:

The 3 dice are all even numbers.
The 3 dice are all odd numbers.

Tip:
To find out if a die number is even you could check whether it is equal to 2, 4 or 6.

Pseudocode:

IF (die1==2 OR die1==4 OR die1==6) AND (die2==2 OR die2==4 OR die2==6) AND (die2==2 OR die2==4 OR die2==6) THEN
   DISPLAY("You have three even numbers.")
END IF

Another method would be to use [lists] and the keyword “in“:

Pseudocode:

IF die1 in [2,4,6] AND die2 in [2,4,6] AND die3 in [2,4,6]  THEN
   DISPLAY("You have three even numbers.")
END IF

Solution...

The solution for this challenge is available to full members!
Find out how to become a member:
➤ Members' Area

Tagged with: Flowchart, Selection

Flowchart to Python Code – Discount Price Calculator

Posted on March 6, 2018 by Administrator Posted in Computer Science, Python - Beginner, Python Challenges

Shopping during the sales can sometimes be very confusing. With discounted prices at 10%, 20%, 50% or even 70%!

For this challenge you are going to write a Python script that prompts the user to enter a price in pounds (or in your own currency) (e.g. £90) and a discount rate to apply (e.g. 20%).

Your program will then calculate and display the discounted price.

We will use the following algorithm for our program:

Python Code

This algorithm is a good example of:

Testing

Once your code is done, complete the following tests to check that your code is working as expected:

Test #	Input Values	Expected Output	Actual Output
#1	Price: £100 Discount Rate: 25%	Discount: £25 Discounted Price: £75
#2	Price: £160 Discount Rate: 40%	Discount: £64 Discounted Price: £96
#3	Price: £180 Discount Rate: 10%	Discount: £18 Discounted Price: £162

Tagged with: Flowchart

Flowchart to Python Code – Temperature Converter

Posted on March 6, 2018 by Administrator Posted in Computer Science, Python - Beginner, Python Challenges, Solved Challenges

Degree Fahrenheit (°F) and Degree Celsius (°C) are the main two units to measure temperature.

The Fahrenheit scale is used mainly in the USA whereas other countries tend to use the Celsius scale.

It is possible to convert a temperature from Celsius degrees to Fahrenheit and vice-versa using the following conversion formulas:

Your Challenge

Use the following flowchart to write a Temperature Converter in Python. Your script will:

Ask the end-user whether they want to convert from Celsius to Fahrenheit or from Fahrenheit to Celsius,
Ask the user to enter a temperature in the correct unit,
Apply the conversion formula and display the temperature in the new unit.

Python Code

This algorithm is a good example of:

Testing

Once your code is done, complete the following tests to check that your code is working as expected:

Test #	Input Values	Expected Output	Actual Output
#1	Option 1 10°C	50°F
#2	Option 1 0°C	32°F
#3	Option 1 -5°C	23°F
#4	Option 2 50°F	10°C
#5	Option 2 32°F	0°C
#6	Option 2 23°F	-5°C
#4	Option x	Invalid option!

Solution...

The solution for this challenge is available to full members!
Find out how to become a member:
➤ Members' Area

Tagged with: Flowchart

Minecraft – Crafting Table

Posted on March 4, 2018 by Administrator Posted in Computer Science, HTML, CSS & JavaScript, JavaScript

For this blog post we have recreated the crafting table in Minecraft using HTML, CSS and JavaScript.

This crafting table enables you to pick up items from your inventory to recreate some of the key recipes to craft new items and add these new items to your inventory.

Our version of the inventory is simplified as it does not record the quantity of items you have left. For each item listed in your inventory it is assumed that you have an infinite supply.

The purpose of this challenge is for you to investigate and reverse engineer how this code works.

First you may want to try this code with a few recipes:

HTML, CSS and JavaScript Code

See the Pen Minecraft Crafting by 101 Computing (@101Computing) on CodePen.

Your Task

You can then adapt this code to add a few more recipes such as the recipe to craft a compass:

And the recipe to craft a clock:

Note that you will find here a full list of Minecraft items.

For more crafting recipes, check this page.

Extra Challenge

The next step would be to tweak this code further to display and update the quantities available for each item in the inventory. These quantities should be reduced when items are used to craft new items, and increased when newly crafted items are added to the inventory.

Data Visualisation Algorithms

Posted on March 1, 2018 by Administrator Posted in A Level Concepts, Computer Science, Computing Concepts, Python - Advanced, Python Challenges

Data visualisation algorithms are used in most software (or video games) which are based on a Graphical User Interface.

They are used to provide a more intuitive, user-friendly visual representation of data.

There is a wide range of techniques and algorithms used to represent data in a visual way, often using Maths concepts (2D or 3D Coordinates, Trigonometry, Proportionality etc.)

The purpose of this blog post is to give examples of a range of data visualisation algorithms.

Example #1: Number of Lives

In a video game, a variable called numberOfLives would be used to store the number of lives remaining, as an integer.
e.g.

numberOfLives = 3

A basic algorithm could then be used to represent this visually at the bottom or top of the screen:

Example #2: Speedometer

Another variable that can be used in a car racing game is the speed of the car in mph.
e.g.

speed = 60

A more advanced algorithm would then be used to represent this value on a speedometer:

Example #3: Analogue Clock

A similar algorithm can be used to represent the time using an analogue clock.

See Python Turtle Clock blog post to implement this algorithm using Python Turtle.

Example #4: Progress Bar

Using linear proportionality we can represent a numerical value as a bar or column.

These three examples would use such an approach to represent data visually:

Progress Bar

Thermometer

Equalizer
See this “Equalizer Animation” blog post to implement this algorithm using HTML, CSS and JavaScript.

Example #5: Pie Charts, Bar Charts, Line Charts, Radar Charts…

Charts are often used to represent data visually. Most high level languages have libraries that can be reused to draw charts.

Try this blog post to draw your own charts using Python Turtle.
Obviously, Python Turtle is not the best library to create charts. Your next step, should you wish to produce advanced charts is to investigate the matplotlib Python library which is very popular to create a wide range of charts. Find out more:

Infographics use a wide range of charts to represent data in a visual way.

Example #6: 2D Representation

Most of the first arcade games where based on a 2D interface.

A 2D interface can be used to represent 2D arrays:

data-visualisation-thatre-booking-system

Theatre Booking System

2D data visualisation algorithms can also be used to represent graphs data structures:

Try the following blog posts to visualise 2D arrays on screen:

Example #6: 3D Representation

Today video games tend to use a 3D user interface which involves more complex data visualisation algorithms.

Try the following blog posts based on 3D data visualisation:

Minecraft Challenge

Example #7: Adding Animation

Data visualisation algorithms can be made more complex when there is a need to animate the visual representation of the data!

Try the following algorithms to create animated simulations:

More examples of Data Visualisation

The following websites contain a wide range of data visualisation techniques:

From Flowcharts to Python Code

Posted on February 28, 2018 by Administrator Posted in Computer Science, GCSE Concepts, Python - Beginner, Python Challenges, Solved Challenges

An algorithm is like a recipe in a cook book. It is a step by step set of instructions that the computer will have to follow to solve a problem or complete a task.

Algorithms consist of step by step instructions which are listed in order and will be executed in the same order, one instruction at a time: this is called sequencing.

On occasions a set of instructions needs to be repeated several times which is done in programming using a loop: this is called iteration.

Computers also have to take decisions as to whether or not to run a set of instructions or to bypass these instructions. In programming these decisions are coded using IF statements: this is called selection.

Complex algorithms can use a range of sequencing, iteration and selection blocks.

To design an algorithm you can draw a flowchart or write pseudo-code.

Your algorithm (flowchart or pseudo-code) can then be converted by a programmer using the programming language of their choice (e.g. Python, Java, Visual Basic, etc.)

Coding Challenges

We have designed five algorithms (See flowcharts below). Your task is to implement each of these algorithms using Python code.

Stopwatch AlgorithmLeap Year?Winter OlympicsTimes TableLogin Form

A stopwatch is used to record the duration of an event as a number of seconds. Our stopwatch algorithm will convert/format this number of seconds to calculate and display the matching number of hours, minutes and seconds, knowing that:

1 hour = 3600 seconds
1 minute = 60 seconds

flowchart-chronometer

Python Code

Complete the code using the trinket below:

This algorithm is a good example of:
sequencing-label

Did you know that the next leap year will be in 2020? To find out if a year (e.g. 2020) is a leap year you can calculate the remainder of year (e.g. 2020) divided by 4. If this remainder is null, then the year is a leap year.

The following algorithm is used to test if a year is a leap year or not.
flowchart-leap-year

Python Code

This algorithm is a good example of:
selection-label

The last Winter Olympics took place in 2018 in Pyeong Chang (South Korea). Winter Olympics take place every 4 years. So when would be the next winter Olympics?

The following algorithm can be used to display the dates of the next ten Winter Olympics.
flowchart-winter-olympics

Python Code

This algorithm is a good example of:
iteration-label

The following algorithm will be used to ask the end-user to enter a number. The program will then display the full times table, from 1 to 10, for this number.
flowchart-times-table

Python Code

This algorithm is a good example of:
iteration-label

A login form should ask the user to enter their username and password. It will then check if these login details are correct before displaying either a welcome message or an error message.
flowchart-login

Python Code

This algorithm is a good example of:
selection-label

Extension Tasks

Use the same approach to complete the following “Flowchart to Python” challenges:

Solution...

The solution for this challenge is available to full members!
Find out how to become a member:
➤ Members' Area

Tagged with: Flowchart

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Your Task…

Web 2.0

Tables, Records & Fields

Primary Keys, Foreign Keys & Relationships

Entity Relationship Diagram (ERD)

SQL Language

To recap…

Python Code

Testing

Extension Task

Solution...

Python Code

Use the above flowchart to help you write the Python code to solve this challenge. This algorithm is a good example of:

Extension Task

Solution...

Python Code

Testing

Your Challenge

Python Code

Testing

Solution...

HTML, CSS and JavaScript Code

Your Task

Extra Challenge

Example #1: Number of Lives

Example #2: Speedometer

Example #3: Analogue Clock

Example #4: Progress Bar

Example #5: Pie Charts, Bar Charts, Line Charts, Radar Charts…

Example #6: 2D Representation

Example #6: 3D Representation

Example #7: Adding Animation

More examples of Data Visualisation

Coding Challenges

Python Code

Python Code

Python Code

Python Code

Python Code

Extension Tasks

Solution...

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Use the above flowchart to help you write the Python code to solve this challenge.

This algorithm is a good example of: