Make sure you read the instructions carefully.
Do not make the easy bits hard by not reading the instructions.
We want the challenge to be in the new things you're learning and trying, not in the reading and paying attention to
what the questions ask.
Don't waste time by trying to save time skim-reading. Just read... and understand... then do.
As you do the early non-coding questions, you can write your answers in a simple text file called questions.txt.
Use whatever text editor you like, but you can use PyCharm to edit text files.
- Write two variable names that would be valid and well-named.
- Write two variable names that would be valid but not well-named.
- Write two variable names that would not be valid.
- What is the naming convention for variables in Python?
- What is a constant? Give an example of when you would use one.
- What is the naming convention for constants?
A drawer contains 10 black and 10 white socks that are all mixed up. What is the fewest number of socks you can take from the drawer without looking and be sure to get a pair of the same colour?
When you've decided on an answer for this, discuss it with a group near you.
If you have a different answer, try and figure out why/how you arrived at different answers.
Is there a meaningful way that you can explain your answer, perhaps a diagram that would help?
As you do individual work on your computer, if you need help, start by talking to your peers.
External students are encouraged to use Slack to ask questions of others in the class.
To use PyCharm as your text editor:
- Run PyCharm
- Open your existing Practicals project (made last prac), or if you don't have it with you for some reason, create a new one following the instructions in the last prac.
- Create a new folder (directory) for
prac_02(remember not to use spaces, and do not make a new project per prac, only new folders). - Now create a new text file: Choose File > New... > File (not Python file)
- Name your file
questions.txt(the.txtextension means PyCharm won't try and correct your Python code... it's just text) - Make sure your new file is inside the prac_02 folder. If it isn't, just drag it in.
Let's walk through a complete example, from problem description, through problem solving to code and testing.
Just read along and understand. Do not "do" any of this, just read it and make sure you understand.
Leia and her friend Han are enjoying a nice meal at a restaurant when they realise it's a public holiday and there's a
surcharge. She wants to find out what the cost of the meal will be including the surcharge.
Leia wants to write a program on her laptop to figure this out but complains that her hands are dirty. Han says, "My
hands are dirty too; what are you afraid of?"
When you break it down and remove the irrelevant parts, you can see this is a simple problem that follows the basic pattern:
- Input
- Processing
- Output
get original_price and surcharge_rate
extra_charge = original_price * surcharge_rate
total_price = original_price + extra_charge
display total_price
We could have done the processing calculation either in one step or two.
Using more steps with good variable names is usually more readable and extensible, but either way is mostly OK.
Also note that here we have used terms written like original_price, valid variable names.
It's fine if you want to use original price or something similar, but doing it like variables means that you can
copy-and-paste your pseudocode and then convert it to Python without rewriting your terms.
Note also that we used the term, surcharge_rate and not just surcharge.
We could have used something like surcharge_percentage, but if we had used just surcharge, we might find it hard to
remember if it means surcharge like 15% (0.15) or like $15 (amount).
Variable names should be unambiguous.
original_price = float(input("Original price: $"))
surcharge_rate = float(input("Surcharge % (e.g. 0.15 is 15%): "))
extra_charge = original_price * surcharge_rate
total_price = original_price + extra_charge
print("The total meal price is $", total_price, sep="")Just because the code is written, doesn't mean it works, so we need to test it. How?
Put in some meaningful/easy inputs so that you can evaluate if the output matches what you expect.
E.g., We can easily calculate that 15% of 100 is 15, so a $100 meal with a 0.15 (15%) surcharge should cost $115.
Original price: $100
Surcharge % (e.g. 0.15 is 15%): 0.15
The total meal price is $115.0
Looks good.
Create a new Python file, example.py (File > New > Python File)
Now, you type this code in (don't copy it), and test it with some other values.
The reason you want to type instead of copy this code is because it helps you learn to use the IDE (e.g. use
autocomplete!), type code accurately, and develop an eye for detail.
Write all of your answers to the following questions in a single Python file called programs.py.
At the top of each program, put a comment with the exercise number/name (copy-and-paste it from
here) so we all know what the program is.
If a question does not require pseudocode, you can use a simple block comment like:
# 4. Deep Sleep Calculation
...The easiest way to write pseudocode for a question is in a multi-line comment like:
"""
2. Kilometres to Miles
get distance_in_kilometres
...
"""
distance_in_kilometres = float(input("Distance in kilometres: "))
...Write a complete Python program that calculates the discounted price of an item given an original price and a fixed
discount of 20%.
Here is the algorithm already done for you in pseudocode:
get original_price
discount = original_price * 0.2
new_price = original_price – discount
print new_price
Test this using meaningful test data that you can understand.
Once you have done this, adjust your program so that 0.2 is a named constant instead of a magic number.
Test it again.
Always test your programs after you modify them. You might have broken something.
We just added another name (the named constant), so check your existing names and see if you need to improve anything.
Remember to follow our teaching
and style guide for good naming.
Now that you've started thinking about constants, you should consider using them appropriately. We won't always tell
you when/if to use a constant,
but you should understand how and when to use constants
.
Use at least one more appropriate constant in your solutions for this practical!
Now that you want to move on to the next exercise, you could start a new file, but instead please just keep using the
same one.
However, you don't want to run the old programs as well as the new one, so you can "comment out" the previous program
code.
To do this, select the lines of code (doesn't need to be exact characters, just any part of the right lines) and
press Ctrl+/ (Windows) or Cmd+/ (Mac).
Note
BEFORE you finalise and submit your practical, you must "uncomment" your finished code.
Joseph has recently moved to Australia from the United States. He understands that distances are given in kilometres
rather than the miles he is used to.
Write pseudocode for a program that will request a distance in kilometres and output the same distance in miles.
Then, implement this algorithm in Python code.
- 1 mile = 1.60934 kilometres
- 1 kilometre = 0.621371 miles
A conversion rate is a good situation to use a constant.
Choose a name that clearly indicates what's being converted to what.
Sonje has been invited on a holiday by her friends, but she is not sure how much it will cost in total.
She knows the cost of the hotel will be $75 per day. (Let's keep it simple and assume days and nights are the same
thing.)
She would like to be able to enter estimates for daily food cost and daily activity cost and then work out the total
based on the number of days for the trip.
For simplicity, assume that each day's costs are the same.
Help Sonje by writing a program that will figure out the total cost for the holiday.
Write pseudocode for this first.
Below is some sample output showing user entry.
Please note that this is what the program looks like when it's finished.
In this example, the user entered 65.50 for the daily food cost, 49 for the activities and 4 for the number of
days (three user inputs).
Note
Whenever we provide sample output, it is a requirement that your solution matches it.
Daily food cost: $65.50
Daily activities cost: $49
Number of days: 4
The trip will cost $758.0
Derek wants to track his quality of sleep and understand what percentage of his night's sleep is "deep".
Deep sleep is when your body and brain waves slow down and is important for proper restoration. Derek has an app that
tracks his sleep but only shows him total time asleep and total time in "deep sleep". He wants to know the percentage of
deep sleep.
Here's an example of version 1 of what the program will look like:
Total sleep in seconds: 161
Deep sleep in seconds : 62
Deep sleep : 1m 2s
Total sleep: 2m 41s
Percentage : 38.50931677018634%
Can you see how this will work? Looks like our I, P, O pattern...
Write a program to produce the percentage based on the two input times (total and deep). This should be easy enough for
you by now...
But wait...
It's not so easy dealing with minutes and seconds like in the example. How do we handle that?
The answer is to develop this program iteratively. Do not try to solve the whole thing in one go. So...
For our first version, let's just use total seconds and ignore the minutes+seconds output.
This will help us focus on the core of the program before we figure out customising the outputs.
- Write a program that asks for the total sleep and the deep sleep in seconds, then displays the percentage.
- Use the same example above to test, so 62 seconds deep, 161 seconds total (short sleep!) should give 0.38509... (don't worry about formatting the output neatly yet).
ONLY when you have that working, can you then focus on enhancing the program.
Keep the inputs the same, but write the output so that it appears as above... How?
Remember how the modulo operation works, and is useful for repeating cycles like time in minutes and seconds?
We know:
161 seconds is 2 minutes and 41 seconds
Because:
161 // 60 = 2
161 % 60 = 41
Also, 0.385 isn't the percentage we want. We want something more like 38.5%. So, what do we need to do to get from 0.385
to 38.5?
(Don't worry about the number of decimal places at this stage; we'll learn about handling that later using string
formatting.)
Knowing this, complete your program so that it outputs like we want. As always, use good variable names.
Before you finish with this file, "uncomment" your previous code for all programs.
Leave the actual comments for headings, but return the rest of the code back to normal.
To do this, select the lines of code and press Ctrl+/ for each program.
PLEASE don't ever comment or uncomment large blocks of code manually by typing or deleting # one at a time. No :)
In questions.txt, type the heading "Reflection" and answer the following questions:
- What is your current career goal? What do you see yourself doing 5 years from now?
- How are your current efforts in this subject helping you achieve that goal?
- What can you differently to improve the value of your time at university as you work towards your goals?
These final sections in practicals are not required to be completed for marks, but you will definitely find benefit in
completing them for extra practice and to extend yourself.
The more practice you do, the more you develop and "lock in" your new skills.
Create a new file, practice.py to complete these tasks in:
Implement the following algorithm for calculating BMI (body mass index):
get height
get weight
bmi = weight / (height ** 2)
display bmi
There is a list of common mathematical operators in your notes.
Write a program that asks the user for two floats called lhs and rhs, then prints the outputs for the expressions
that use those numbers and a maths operator.
Note that we are OK with a variable name like lhs here because:
- it's a very common abbreviation for "left hand side"
- it is unambiguous in this context
- there is no better, more obvious name (e.g. it doesn't mean
ageorscoreor anything else)
Example, if the user enters 2.5 and 3, it would print:
2.5 + 3.0 is 5.5
2.5 * 3.0 is 7.5
2.5 // 3.0 is 0.0
...
Use as many operators as you can - not just these ones.
Write as many programs as you can handle that convert values in one unit of measurement to another, such as (and the reverse):
- kilograms to pounds
- fahrenheit to celsius
- feet and inches to metres and centimetres
- currencies...
If you're cruising and want more of a challenge, look up how to do string formatting so that you can produce neatly lined up output with a fixed number of decimal positions for the above programs, especially the deep sleep one.
This section summarises the expectations for marking in this practical.
Please follow the submission guidelines to ensure you receive marks for your work.
Files required:
questions.txt with:
- Quick Questions
- Logic Exercise
- Reflection
programs.py with:
- Discount Price
- Kilometres to Miles
- Holiday Cost
- Deep Sleep Calculation (Percentage)