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Hello, my name is Mrs. Holborow and welcome to Computing.
I'm so pleased that you've decided to join me for the lesson today.
In today's lesson, we're going to use our understanding of data structures to complete a project.
Welcome to today's lesson from the unit "Python programming with sequences of data." This lesson is called "Data structure projects in Python." And by the end of today's lesson, you'll be able to apply your understanding of data structures and iteration to investigate a problem.
It would be useful if you have access to a device that you can create and amend coding for this lesson.
Shall we make a start? We will be exploring these keywords during today's lesson.
Investigate.
Investigate.
Examine data carefully to find out the truth about something.
Rounding.
Rounding.
Reducing the number of digits in a number by examining the digits that follow that will be discarded.
Today's lesson is split into two sections.
We'll start by planning how to investigate data and then we'll move on to solve a problem using code.
Let's make a start by planning how to investigate data.
Data structures, like lists, can be used to store large quantities of data that can be used by programmers.
For example, a list could hold temperatures recorded by a data logger.
Data can be investigated to prove or disprove a theory or hypothesis.
For example, average temperatures are increasing.
Help to spot patterns.
Average temperatures over the last 20 years have increased.
Help to identify issues or problems. Climate change is affecting our planet, average temperatures are increasing.
Provide evidence that can be used to support a cause.
The data shows that average temperatures over the last 20 years have increased.
If you had a list of temperatures, what problems could you investigate? Perhaps pause the video here and have a think.
Ah, here's Lucas with an answer.
Lucas says, "I could investigate how temperatures have changed over the last 10 years to see if the climate is getting warmer." That's a great response, Lucas.
Sam's got an answer too.
Sam says, "I could investigate how much the average temperature has changed in July over the past five years." That's another great idea, Sam.
Well done.
When investigating a problem that will be solved using code, it's useful to know the software development life cycle.
So because this is a life cycle, it continually flows and we could keep going round and round throughout the project development.
So we start with planning.
We then move on to analysis.
We then design.
After we design, we go on to development and then testing, and then we implement the solution.
Let's have a look at each of these stages in a bit more detail.
So for planning, we ask the question, what are we trying to investigate? What are we trying to prove or disprove? For analysis, we consider, what data do we need? And where will we get that data from? In design, we'll look at how we will solve the problem and what algorithms we may need to develop.
Here's some sample answers from Sam.
For planning, Sam says, "I'm investigating how much the average temperature has changed in July over the past five years." In the analysis section, Sam says, "I need the daily temperatures for July for the past five years.
I can find this information on the internet." Design, "I will create lists containing the temperatures in July for each year.
I'll then iterate through each of the lists to calculate the average for each year." The development section is where we actually write the code to solve the problem.
And then for testing, we check that our code works correctly and whether or not we need to fix any errors or bugs in the code.
And then for implementation, we complete the solution.
And then we ask ourselves, what does the solution tell us? Here's some more sample answers from Sam.
For development, Sam says, "I've created my code in Python." For testing, "My programme didn't work correctly the first time as I forgot to put brackets around a calculation.
I added these in and then the average was calculated correctly." For implementation, Sam says, "My investigation showed that average temperatures in July have increased over the last five years." Time to check your understanding.
At which stage of the software development life cycle would you write your code? A, testing; B, design; or C, development? Pause the video whilst you have a think.
Did you select C, development? Well done.
These lists hold some data about forests in England over the past 10 years.
So we've got two separate lists here.
One called planted, and one called cut.
The planted list contains the amount of new forest planted in thousands of hectares, and the cut list contains the amount of forest cut down again in thousands of hectares.
What could you investigate using this data? Perhaps pause your video here and have a think.
Time to check your understanding.
Which of the following could you not investigate using the forestry data? A, how many visits were made to the forest.
B, how many hectares have been planted in total over the past 10 years.
Or C, in what year the most amount of forest was cut down.
Pause the video whilst you have a think.
That's right, you couldn't investigate how many visits were made to the forest because our lists and data doesn't contain this information.
Okay, you're doing a fantastic job so far, so well done.
We're moving on to our first task of today's lesson, which is Task A.
So for part one, in Task B, a bit later on in today's lesson, you're going to use the forestry data to prove or disprove the following statement.
"Forest areas in England are declining." Use the questions below to plan out your investigation.
So A, planning, what will you investigate using the data? So what question or problem are you trying to investigate? B, analysis, what data will you need? And C, design, how will you solve the problem? Pause the video here whilst you complete the activity.
How did you get on? Let's have a look at a sample answer together.
So for part A, you were asked to look at the planning stage.
So what is it that you're trying to investigate? I will use the data to investigate whether the local amounts of forest area in England have increased or decreased.
For the analysis section, what information or data do we need? I'll find the total forest area planted and the total forest area cut down for each year.
For part C, design, how are we gonna go about investigating the problem? So sample answer here, I will calculate the total net forest area for each year.
I'll use a for loop to iterate through the list items and subtract the forest area cut from the forest area planted and add this amount to a total.
I'll then be able to clearly see if the total forest areas have increased through planting or decreased through cutting.
I'll also be able to see which years were better for increasing forest areas than others.
Remember, your answer doesn't have to be exactly the same as this, but if you want to go back and change your answer or add any detail, then you can do that now.
Okay, we're moving on to the second part of today's lesson where we're going to solve a problem using code.
Lucas says, "I'm going to investigate whether the areas of forest in England have increased over the last 10 years." Sam says, "That's a great idea.
What list methods could you use to help you find the answer?" The following Python list operations can be used to alter data held in a data structure.
list.
append(item) So the item that we're going to add, we put inside the brackets.
list.
insert(index, item) So this will insert an item in a set position in the list, whereas the list.
append will just add the item onto the end of the list.
list.
pop(index) will remove a specific item in a list.
And list.
remove will remove a specific item by name rather than index number.
These operations are really useful if you want to add or remove any data from a list.
Time to check your understanding.
Match the operation to the correct description.
Pause the video whilst you have a think.
How did you get on? Did you manage to match them correctly? Let's have a look at the answers together.
list.
append(item) will add an item to the end of a list.
list.
insert(index, item) will add an item at a set index position.
list.
pop(index) will remove an item at a set index.
And then finally, list.
remove(item) will remove a specific item.
Did you get all of those correct? Well done.
The following Python list operations can be used to analyse data held in a data structure.
list.
count(item) to count how many times an item appears in a list.
list.
index(item) so return the index value of a particular item in a list.
list.
sort() which will put the items in ascending order.
And then list.
sort(reverse=True) which will put the items in descending order.
These list operations can help you to answer questions about data.
Time for another check.
Match the operation to the correct description.
Pause the video whilst you have a think.
How did you get on? Let's have a look at the answers together.
list.
count(item) will get the number of occurrences of an item.
list.
index(item) will search for the index of an item.
list.
sort() will sort the list items in ascending order, and then list.
sort(reverse=True) will sort the items in descending order.
In Python, numbers with decimal points are stored as floats.
When performing calculations on floats, you can often end up with numbers with multiple digits after the decimal point.
This is because of the way how floating-point numbers are stored in Python.
You can reduce the number of digits after the decimal point by rounding.
Rounding a number will reduce the number of digits.
So here I've got a snippet of code.
So I've got my two lists that we've seen already in today's lesson, planted and cut, and then on line 7 I've got a for loop.
So the for loop goes through each item in the planted list and it gets a position number, so planted.
index(item) and it holds that item as position.
So for example, the first item in the list will be position 0.
And then on line 9 we've got total = planted[position] - cut[position] So for the first time around the for loop, this will be the first item in the planted list and the first item in the cut list, position 0.
On line 10, we've then got a variable called total which says it's equal to round(total, 2).
So the key bit here is we're using the round() function to round the total down to two decimal places.
On line 11, we're just printing out that total.
So you can see that the code round() function is rounding the value held by the variable total to two decimal places.
And if we have a look at the sample output here, you can see that it's rounded it down to two decimal places.
So we've got -3.
04.
Lucas says, "I've started to write the code to investigate my data, but it's not working as I expected." Sam says, "That's the whole point of testing.
Don't worry, look at each line of code and see if you can spot any errors." That's some really good advice, Sam.
It's common for a programme not to work as expected the first time you run it.
Testing is an important part of programming and some top tips for testing include checking that your programme does not include any syntax errors.
For example, a missing bracket or a speech mark.
Check that the indentation is as expected.
For example, in an if statement or a loop.
Check that the programme is accessing the index of the correct item in a list.
Have you started at position 0? Check that the logic for the programme is correct.
For example, has the correct operator been used? For example, less than or more than? Okay, we're now moving on to our second set of tasks for today's lesson and you've done a fantastic job so far, so well done.
Open the starter programme at oak.
link/forestry-data.
The forestry data for this year has been released.
3.
03 thousand hectares were planted and 2.
89 thousand hectares were cut down.
Append these amounts to the correct lists.
For part three, for each year, record the difference between the total hectares planted and the total hectares cut down.
This is the net forest gain or loss.
Pause the video here whilst you complete the activity.
How did you get on? Did you manage to complete the activities? Well done.
So you were asked to open the starter file and start by adding in the two new pieces of data from this year.
So you can see on line 7 and 8 we've got planted.
append(3.
03) and on line 8 we've got cut.
append(2.
89) You were then asked to calculate the net forest gain or loss for each year, and that's been done inside the for loop.
If you want to have a look at the solution in more detail, you can go to oak.
link/forestry-data-solution.
Let's have a look at the answers that you should have.
So for year one, the net forest gain should be -3.
04.
Year two, -2.
87, so these are all losses.
Three, -2.
79.
Year four, -2.
79 again.
Year five, -1.
96.
Year six, -2.
01.
Year seven, -0.
81.
Year eight, -2.
06.
Year nine, -2.
39.
And then in year 10, we have our first gain, so 0.
67.
And year 11, another gain of 0.
14.
Remember, if your answers don't quite match these, you can go back and you can correct your code.
I'd now like you to calculate the total net forest gain or loss over the 11-year period.
Test your programme to make sure it works as expected, and if it doesn't, correct any errors.
What does the data tell you about forest areas in England? And finally, what do you notice about the last two years? Pause the video whilst you answer the questions.
How did you get on? You were asked to calculate the total net forest gain or loss.
Hopefully you've got the answer -19.
91.
And this was done using this snippet of code here.
So we've got a new variable called net, what we've said inside the for loop is equal to net + total.
So each time we go through the for loop, we're adding the value of total to the value held by net.
And then outside of the for loop, on line 17, we've said net = round(net, 2) so decreasing it to that two decimal points.
And then finally, on line 18, we're returning or printing out the value of that net variable, which should be -19.
91.
For part six, you were asked, what does the data tell you about forest areas in England? Here's a sample answer.
The total net forest gain or loss was 19.
91 thousand hectares, which shows that in England, more areas of forest have been lost than gained.
For part seven, you were asked, what did you notice about the last two years? The last two years were the only years the net forest gain/loss was positive, so more areas of forest were planted in these years than were cut.
Perhaps this shows that our forest loss is being reduced, which would be a good thing for our environment.
Well done, we've come to the end of today's lesson and you've done a fantastic job, so great work.
Let's summarise what we have learned together.
Data can be used to investigate a problem.
Programming tools can be used to perform investigations on data held in data structures.
When investigating a problem that will be solved using code, it's useful to follow the software development life cycle.
I hope you've enjoyed today's lesson and I hope you'll join me again soon, bye.
