Molecular Mass Calculator

Posted on January 26, 2015 by Administrator Posted in Computer Science, Python - Advanced, Python Challenges, Solved Challenges

Learning Objectives

In this challenge you will improve your string manipulation techniques as well as use Python to perform some basic mathematical calculations.

Did you know?

The molecular weight (mass) may be calculated from the molecular formula of the substance; it is the sum of the atomic weights of the atoms making up the molecule. The molecular mass is expressed in atomic mass unit (amu).

For example, water has the molecular formula H₂O, indicating that there are two atoms of hydrogen and one atom of oxygen in a molecule of water.

Atom	Atomic Mass	Quantity	Total Mass
H	1.008	2	2.016
O	15.999	1	15.999
H₂0			18.015

In the following script we use a Python dictionary called atomicMass to store the atomic mass of some of the main atoms (C, H, O…)

We then work out the molecular mass of water: H₂0.

Your Challenge

Adapt this script to get the program ask the end-user to enter a molecular formula of their choice.
Using string manipulation techniques your Python script will break down the formula entered by the end-user and calculate the total mass of the molecule.

Test your script with the following molecules:

Molecule	Formula
Water	H₂O
Carbon Dioxide	CO₂
Methane	CH₄
Butane	C₄H₁₀
Carbonic Acid	H₂CO₃
Acetone	CH₃COCH₃
Lactose	C₁₂H₂₂O₁₁

Challenge #2

Add more atoms to the atomMass dictionary as follows:

Atom	Atomic Mass
Fe	53.939
Ag	106.905
Cu	62.929
Na	22.989
Cl	34.968

Adapt your script so that it recognises when these atoms are used by the end-user when entering their molecular formula. This will be based on the use of uppercase & lowercase letters.

Test your script with the following molecules:

Molecule	Formula
Sodium Chloride	NaCl
Iron Oxide	Fe₂O₃
Copper Chloride Hydroxide	HOCuCl

Solution...

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Tagged with: Python Challenge, String Manipulation

My Conversion Library

Posted on January 25, 2015 by Administrator Posted in Computer Science, Python - Intermediate, Python Challenges, Solved Challenges

conversion

Learning Objectives

In this challenge you will learn how to create your own library and how to use it in your programs.

A library is a collection of functions and procedures. A library can then be reused in all your programs using the import instruction.

You have most likely used some libraries in the past, for instance the random library or the maths library.

We are going to create our own library focusing on conversion formulas. It will be useful when we need to convert for example distances from one unit to another (e.g. miles to km, cm to inches).

We have started the library for you by defining two functions: kmToMiles() and milesToKm().

Your Challenge

Complete the library to add the following conversion functions (Roll-over the frames below to reveal the conversion formula):

Converting Distances

Converting Temperatures

Converting Weights

Time Conversion

Solution...

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Lightning Distance Calculator

Posted on January 24, 2015 by Administrator Posted in Computer Science, Python - Beginner, Python Challenges, Solved Challenges

Have you ever seen a lightning flash or heard the thunder of lightning and wondered how close you were from the ligthning strike? Have you noticed that there is always a delay between the flash of light and the clap of thunder when a lightning occurs?

It is possible to calculate the distance to a ligthning strike by counting the seconds between the lightning flash and the sound of thunder.

When lightning strikes, the first thing you see is the flash of light which you can see instantly. This is because light travels at a very high speed (Speed of light = 300,000 km/s). At the same time a clap of thunder is created. However, in the air a sound wave does not travel as fast as light, so it may take a few seconds for this clap of thunder to reach you. This depends on how far you are from the lightning.

Look at the following diagram and check the formula of speed. Bear in mind that the speed of a sound wave in the air is 340 m/s.

Your Challenge

Write a Python program that asks the end-user to enter a number of seconds. The program should output the distance (in meters or kilometres) from the lightning strike.

Note that 1 mile = 1.609 km, you may want to convert this distance in miles.

Solution...

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Tagged with: Python Challenge

Space Mission

Posted on January 24, 2015 by Administrator Posted in Computer Science, Python - Intermediate, Python Challenges

Rosetta: Rendez-vous with a comet

Rosetta is a robotic space probe built and launched by the European Space Agency. Along with Philae, its lander module, Rosetta is performing a detailed study of comet 67P/Churyumov–Gerasimenko.
Rosetta_spacecraft

Rosetta

Philae

Comet 67P
Rosetta: © (CC) ESA/ATG medialab – https://www.flickr.com/photos/europeanspaceagency/11206647984/
Philae: © (CC) ESA/ATG medialab – https://www.flickr.com/photos/europeanspaceagency/10796307373/
Comet 67P: © (CC) SA/Rosetta/NAVCAM – http://blogs.esa.int/rosetta/2014/09/19/cometwatch-19-september/

Your Challenge

At the time this blog post was created, the European Space Agency just received new photographs of comet 67P taken by Rosetta. The spaceship was 500 million km away from Earth.

Write a Python script to answer the following question:

Considering that electro-magnetic signals used to communicate with Rosetta travel at the speed of light (300,000 km/s), how long did these pictures take to travel from Rosetta to planet Earth?

To help you solve this problem you may need to investigate the following formulas:
speed-formula
You will need to make sure your script gives the answer using in the correct format: hh:mm:ss.

Challenge #2: Time travelling?

Did you know that when you look at the stars in the night sky you are time travelling. You are in fact looking at what the stars did look like years and years ago! This is because the stars are extremely far away from planet Earth, and the light they create takes several years to reach us.

When astronomers measure the distance of stars (from planet Earth) they do not use the kilometer (km) unit but instead they use the light-year unit. One light-year represents the distance that light travels in one year, at the speed of light (300,000 km/s).

Your challenge consists of writing a Python script to calculate the distance in km of one light-year.

Then you will use your script to calculate the distance in km for the following stars:

Star	Distance from Earth (in light-years)
Alpha Centauri	4.24 light-years
Barnard’s Star	5.96 light-years
Luhman 16	6.59 light-years
WISE 0855-0714	7.2 light-years
Wolf 359	7.78 light-years

Source:
http://en.wikipedia.org/wiki/List_of_nearest_stars_and_brown_dwarfs

Discount Price Calculator

Posted on January 23, 2015 by Administrator Posted in Computer Science, Python - Beginner, Python Challenges, Solved 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.

Video Tutorial

Python Code

Complete the code provided below:

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

Solution...

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Fahrenheit to Celsius Converter

Posted on January 23, 2015 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

Write a Python script to:

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

Testing

You can now use your code to complete the following test plan to test your code:

Celsius degrees to Fahrenheit conversions:

Test #	Input Values (°C)	Expected Output (°F)	Actual Output
#1	20	68
#2	-10	14
#3	0	32

Fahrenheit to Celsius degrees conversions:

Test #	Input Values (°F)	Expected Output (°C)	Actual Output
#1	68	20
#2	14	-10
#3	32	0

Challenge #2

On the temperature scale, the 0°C (=32°F is called Freezing Point which is when water starts freezing and becomes ice. At 100°C (=212°F) water starts to boil. This is called Boiling Point.

Adapt your script to write a message to the end user as follows:

You are above boiling point for all temperatures above 100°C
You have reached boiling point if the temperature is exactly 100°C
You are between freezing point and boiling point for all temperatures between 0°C and 100°C
You have reached freezing point if the temperature is exactly 0°C
You are below freezing point for all temperatures below 0°C

Solution...

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Tagged with: Python Challenge

The legend of the chessboard

Posted on January 23, 2015 by Administrator Posted in Computer Science, Python - Beginner, Python Challenges, Solved Challenges

The story tells us that long long ago the great Sultan of India loved to play games. As he started to get bored of the games that were present at the time he asked a wise man who lived in his kingdom to come up with a new game.

This, according to the legend, is how the game of chess was invented. The Sultan was very pleased with the wise man who had invented the game and in return he offered the wise man a reward of his own choosing.

To the Sultan’s surprise, the wise man did not ask for any gold. Instead he only had one request: He asked just for a few grains of rice in the following manner: the sultan was to put a single grain of rice on the first chess square, two grains on the second square, four on the third square and carry on doubling this number on every consequent square to fill up all 64 squares of the chessboard.

This seemed to the ruler to be a modest request, so he called for his servants to bring the rice. Did the Sultan manage to fulfil the wise man’s request?

Python Code

Your task consists of writing a python script to calculate the total number of grains of rice required to cover the chessboard following’s the wise man’s request.

Solution...

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Tagged with: iteration, Python

Fraction Simplifier

Posted on January 22, 2015 by Administrator Posted in Computer Science, Python - Advanced, Python Challenges, Solved Challenges

This challenge consists of writing a program that asks the end-user to enter a fraction (numerator and denominator) and output the matching reduced fraction when the fraction can be reduced.

To see what this program should do in action you may want to try fractionsimplifier.com.

$fraction_numerator_denominator$

To simplify a fraction your program will need to find the greatest common divisor (aka greatest common factor) of the numerator and denominator that will have been entered by the end user. Then, your program will divide the numerator and denominator of the fraction by this number.

$fraction$

To find out if a number is a factor of the numerator you will need to check that the remainder of the numerator divided by this number is null (=0):

For instance 3 is a factor of 24 because 24 mod 3 = 0.

Whereas 5 is NOT a factor of 32 because 32 mod 5 = 2 != 0.

Extra tip: A factor of a number is always lower or equal to this number.

Your Challenge:

Complete the code below to find the greatest common factor of both the numerator and denominator entered by the end-user and use it to output the simplified fraction.

Solution...

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Tagged with: iteration, Python Challenge

Area Calculator

Posted on January 19, 2015 by Administrator Posted in Computer Science, Python - Beginner, Python Challenges, Solved Challenges

For this challenge we are going to use a Python script to calculate the area in square meters of two different flats.

To do so we will write a computer program that will add up all the areas of each room.

Most rooms have a rectangle shape. So we will first define a function that takes two parameters: width and length and return the area of the rectangle using the following formula:

area = width * length

Let’s use this formula to calculate the area of this small flat:

Your Challenge

Tweak the code above to calculate the area of the following two flats: (Click on each picture to zoom in).

Challenge #2

The area of a right-angled triangle can be calculated as follows:

area = width * length / 2

Add a new function called getTriangleArea to return the area of a right-angled triangle using two parameters: width and length.

Use both the getRectangleArea and getTriangleArea functions to calculate the area of this room:

Challenge #3:

Use your code to calculate the area of this small mansion (Click on picture to zoom in):

Solution...

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Tagged with: Function, Parameter, Python Challenge, subroutine

3D Challenge

Posted on January 14, 2015 by Administrator Posted in Computer Science, Python - Advanced, Python Challenges, Solved Challenges

The aim of this challenge is to draw a cube in 3D and to make it rotate on the screen.

Drawing 3D shapes on a screen (2D) requires some mathematical formulas to convert 3D (x,y,z) coordinates into 2D coordinates (x,y). This conversion, also known as “oblique projection” is based on the following formulas:

This is a great application of trigonometry, especially of the SOCATOA formulas!

(Read more about trigonometric formulas.)

A 3D rotation against an axis (X, Y or Z axis) also requires some complex mathematical formulas. To apply a 3D rotation we can use the rotation matrix as follows:

Our Solution:

To decide the angle and axis of rotation we use the position of the mouse pointer.
The X coordinate of the mouse pointer becomes the angle of rotation against the Y axis.
The Y coordinate of the mouse pointer becomes the angle of rotation against the X axis.
In this example we did not implement a rotation against the Z axis.

Your Task

Add more edges to the code given above to create a full house including a roof, a front door and a window.

Solution...

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Tagged with: 3D, Coordinates

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Learning Objectives

Did you know?

Your Challenge

Challenge #2

Solution...

Learning Objectives

Your Challenge

Converting Distances

Converting Temperatures

Converting Weights

Time Conversion

Solution...

Your Challenge

Solution...

Rosetta: Rendez-vous with a comet

Your Challenge

Challenge #2: Time travelling?

Video Tutorial

Python Code

Testing

Solution...

Your Challenge

Testing

Challenge #2

Solution...

Python Code

Solution...

Your Challenge:

Solution...

Your Challenge

Challenge #2

Challenge #3:

Solution...

Our Solution:

Your Task

Solution...

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