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Assignment 3
1/13
Assignment 3
Due Apr 8 by 6p.m.
Points 0
Available Mar 22 at 12a.m. - Apr 8 at 11:59p.m.
Hypertension and Low Income in Toronto
Neighbourhoods
Goals of this Assignment
In this assignment, you will practise working with files, building and using dictionaries, designing
functions using the Function Design Recipe, reading documentation, and writing unit tests.
No Extensions
Please, note that NO EXTENSIONS are allowed for this assignment, since it is due on the last day of
classes. Only AccessAbility requests and illness- or emergency-related requests will be accepted.
Please, submit these by email to Purva, the course coordinator, with appropriate documentation.
Background
A commonly-held belief is that an individual's health is largely influenced by the choices they make.
However, there is lots of evidence that health is affected by systemic factors.
Health researchers often study the relationships between an individual's health outcomes and factors
related to their physical environment, social and economic situations, and geographic location.
Studies such as this one (https://doi.org/10.1161/CIRCRESAHA.120.318729) investigate how a
particular health outcome (living with hypertension) are tied to a systemic factor (the income level of a
country).
In this assignment, you will write code to assist with analyzing data on the relationship between
hypertension (also known as high blood pressure) and income levels in Toronto neighbourhoods. The
data you will work with is real data, however we have simplified it somewhat to make this assignment
clearer for you.
A note on math and stats
The data analysis that your code will do will include some statistical analysis that we have not talked
about in the course. You do NOT need to understand the underlying statistics to complete this
assignment. The code you write will do some simple mathematical operations, like adding up some
numbers, or finding ratios using division. We will use Pearson correlation for the more advanced
analysis and you will use existing functions that we have imported for you.
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You will need to take a look at the examples of these functions in order to figure out what arguments
you need to pass to them, and what types of data they return, but you do not need to understand how
they work in any detail.
Correlation is a single coefficient expressing the tendency of one set of data to grow linearly, in the
same or opposite direction, with another set of data. This is done by comparing whether points that
have been paired between the two sets are similarly greater or less than than their set's respective
averages.
For example, if we wanted to compare whether for students in the class, age is correlated with height,
we would have two sets of data, birth date (which we could express as, say, number of weeks old for
finer granularity), and heights.
Numbers from each set are ordered in the same way so that each height value corresponds to the
age value for the same student. What is nice about the correlation metric we are using, is that it is
normalized to be between -1 and 1, with these values giving us a nice human interpretation. A value
of 1 means that the points make a straight line. In our example, this means, for some increase in age,
we have a consistent increase in height. Similarly, a value of -1 is the same relationship but with a flip
of direction, where older students would be shorter than younger ones. Finally, a value of 0 would say
that there is no consistent increase or decrease in height for a change in age. We will use this to
investigate the relationship between low income rates and hypertension, for any tendency to increase
or decrease together.
If you are a statistics person, keep in mind that the learning goals of the assignment are about writing
code using what we've learned in the course, not about doing a proper statistical analysis.
Dataset descriptions
This assignment uses data files related to one of the two variables of interest (i.e., hypertension data
or income data). The files are CSV (comma separated values) files, where each column in a line is
separated by a comma. You can assume there are no commas anywhere else in the files, other than
to separate columns, and that any file given is in the correct format. The two file types are described
below.
Neighbourhood hypertension data files
The first row in a neighbourhood hypertension file contain header information, and the remaining
rows each contain data relating to hypertension prevalence in a particular Toronto neighbourhood.
Here is a description of the different columns of the dataset. Notice the use of constants and carefully
study the starter file constants.py .
Neighbourhood hypertension dataset
Column index Description
HT_ID_COL An ID that uniquely identifies each neighbourhood.
HT_NBH_NAME_COL The name of the neighbourhood. Neighbourhood names are unique.
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HT_20_44_COL The number of people aged 20 to 44 with hypertension in the neighbourhood.
NBH_20_44_COL The total number of people aged 20 to 44 in the neighbourhood.
HT_45_64_COL The number of people aged 45 to 64 with hypertension in the neighbourhood.
NBH_45_64_COL The total number of people aged 45 to 64 in the neighbourhood.
HT_65_UP_COL The number of people aged 65 and older with hypertension in the neighbourhood.
NBH_65_UP_COL The total number of people aged 65 and older in the neighbourhood.
Neighbourhood income data files
The first row in a neighbourhood income data file contains header information, and the remaining
rows each contain data about low income status.
Here is a description of the different columns of the dataset. Notice the use of constants and carefully
study the starter file constants.py .
Neighbourhood income dataset
Column index Description
LI_ID_COL An ID that uniquely identifies each neighbourhood.
LI_NBH_NAME_COL The name of the neighbourhood. Neighbourhood names are unique.
POP_COL The total population in the neighbourhood.
LI_POP_COL The number of people in the neighbourhood with low income status.
Neighbourhood names and ids are the same between our hypertension data files and our low income
data files. However, the total population of a neighbourhood can be different between the two data
files, as they were collected at different times.
The CityData Type
The code you will write for this assignment will build and then use a dictionary that contains
hypertension and low income data about neighbourhoods in a city. This section describes the format
of that dictionary.
Key/value pairs in a CityData dictionary
Each key in a CityData dictionary is a string representing the name of a neighbourhood. As is
necessary for dictionary keys, all neighbourhood names will be unique.
The values in a CityData dictionary are dictionaries containing information about a neighbourhood.
These neighbourhood data dictionaries contain specific keys that label a neighbourhood's data.
Format of the inner dictionaries
A dictionary that is a value in a dictionary of type CityData has the following key/value pairs. Notice
the use of constants and carefully study the starter file constants.py .
CityData dictionary
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Key (Type) Value
ID ( int ) The id number of this neighbourhood.
TOTAL ( int ) The total population of this neighbourhood, as given in the low income data file.
LOW_INCOME ( int ) The number of people in this neighbourhood who are classified as low income.
HT
( list[int] ) A list of the hypertension data of this neighbourhood. This list will have
length exactly 6, and the values will be the numbers from
columns HT_20_44_COL , NBH_20_44_COL , HT_45_64_COL , NBH_45_64_COL , HT_65_UP_COL ,
and NBH_65_UP_COL stored at
indices HT_20_44_IDX , NBH_20_44_IDX , HT_45_64_IDX , NBH_45_64_IDX , HT_65_UP_IDX ,
and NBH_65_UP_IDX of the list, correspondingly. See the section above on
neighbourhood hypertension data files.
An example CityData dictionary
The following is an example of a CityData dictionary. We have also provided this dictionary for you to
use in your docstring examples and other testing in the starter code file. Note that we have formatted
the dictionary below for easier reading, however you will not see this formatting in your code.
{'West Humber-Clairville': {
'id': 1,
'hypertension': [703, 13291, 3741, 9663, 3959, 5176],
'total': 33230,
'low_income': 5950},
'Mount Olive-Silverstone-Jamestown': {
'id': 2,
'hypertension': [789, 12906, 3578, 8815, 2927, 3902],
'total': 32940,
'low_income': 9690},
'Thistletown-Beaumond Heights': {
'id': 3,
'hypertension': [220, 3631, 1047, 2829, 1349, 1767],
'total': 10365,
'low_income': 2005},
'Rexdale-Kipling': {
'id': 4,
'hypertension': [201, 3669, 1134, 3229, 1393, 1854],
'total': 10540,
'low_income': 2140},
'Elms-Old Rexdale': {
'id': 5,
'hypertension': [176, 3353, 1040, 2842, 948, 1322],
'total': 9460,
'low_income': 2315}}
The sample CityData dictionary above represents hypertension and low income data for five
neighbourhoods: West Humber-Clairville, Mount Olive-Silverstone-Jamestown, Thistletown?Beaumond Heights, Rexdale-Kipling, and Elms-Old Rexdale.
Let's take a closer look at the data for Elms-Old Rexdale. This neighbourhood is represented by the
key/value pair where the key is 'Elms-Old Rexdale' . The id of this neighbourhood is 5. The
hypertension data for this neighbourhood is as follows: 3353 people are between the ages of 20 and
44, 176 of whom have hypertension. There are 2842 people between the ages of 45 and 64, 1040 of
whom have hypertension, and there are 1322 people aged 65 and up, 948 of whom have
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hypertension. The low income data for this neighbourhood is that 2315 people are classified as low
income, from a total population of 9460 people.
Note that the totals do not match between the low income and the hypertension data this is
because the low income data was collected before the hypertension data, and the size of the
neighbourhoods changed. For the purposes of this assignment, we will assume the collection of
these two datasets is close enough in time to compare them to each other. You do not need to do
anything about these differing totals, other than to make sure you are using the correct total when
computing rates, as described later.
Age standardisation
This section describes the process of age standardisation that we will use in this assignment to
perform a more accurate analysis. Note that we have given you a function that computes the age
standardised rate from the raw rate (described in Task 3). This section is for your information
only; we have already implemented this for you.
Our dataset will let us calculate the rate of hypertension in each Toronto neighbourhood. One
complicating factor is that different neighbourhoods have different age demographics. For example,
the Henry Farm neighbourhood has a significantly lower proportion of 65+ residents than Hillcrest
Village. And because people aged 65+ have a higher overall rate of hypertension, this demographic
difference alone would cause us to expect to see a difference in the overall hypertension between
these neighbourhoods.
So because we care about the impact of low income status on hypertension rates, we want to remove
the impact of different age demographics between the neighbourhoods. To do so, we will use a
process called age standardisation to calculate an adjusted hypertension rate that ignores differences
in ages. This process involves the following steps for each neighbourhood:
1. First, we'll calculate the hypertension rate within each of the following age groups: 20-44, 45-
64, and 65+. We'll report these rates as percentages, which you can think of as being the
number of cases of hypertension per 100 people aged 20-44 / 45-64 / 65 and up.
2. Then, we'll pick one standard population with certain numbers of people in these age groups.
For the purpose of this assignment, we'll use the total Canadian population from the 1991
census: (https://www12.statcan.gc.ca/English/census96/data/tables/Rp-eng.cfm?
LANG=E&APATH=3&DETAIL=1&DIM=0&FL=A&FREE=1&GC=0&GID=0&GK=0&GRP=1&PID=1029&
Population by age
group data
Age GroupPopulation
20-44 11,199,830
45-64 5,365,865
65+ 3,169,970
Total (20+) 19,735,665
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1. Then, we'll use the neighbourhood rates to calculate the hypothetical number of people in the
standard population who would have hypertension. For example, if the rates for neighbourhood X
were 20% of 20-44, 30% of 45-64, and 66% of 65+, the total number of people with hypertension
in the standard population would be 2,239,966 + 1,609,760 + 2,092,180 = 5,941,906 .
2. Finally, divide this number of people with hypertension by the total size of the standard population,
yielding a final percentage 5,941,906 / 19,735,665 x 100 or approximately 30% . This percentage
is the age standardised rate for the neighbourhood.
If you are interested, you can read more about age standardised rates here
(https://www.statcan.gc.ca/en/dai/btd/asr) .
Required Functions
In the starter code file a3.py , follow the Function Design Recipe to complete the functions described
below.
You will need helper functions (i.e., functions you define yourself to be called in other functions) for
some of the required functions, but likely not for all of them. Helper functions also require complete
docstrings with doctests. We strongly recommend you also follow any suggestions about helper
functions in the table below; we give you these hints to make your programming task easier.
Some indicators that you should consider writing a new helper function, or using something you've
already written as a helper are:
Rewriting code to solve a task you have already solved in another function
Getting a warning from the checker that your function is too long
Getting a warning from the checker that your function has too many nested blocks or too many
branches
Realizing that your function can be broken down into smaller sub-problems (with a helper function
for each)
For each of the functions below, other than the file reading functions in Task 1, write at least two
examples in the docstring. You can use the provided SAMPLE_DATA dictionary, and you should also
create another small CityData dictionary for examples and testing. If your helper function takes an
open file as an argument, you do NOT need to write any examples in that function's docstring.
Otherwise, for any helper functions you add, write at least two examples in the docstring.
Your functions should not mutate their arguments, unless the description says that is what they do.
Assumptions
Assume the following about the data:
All neighbourhood ids and names are unique, and will appear the same in all data files. That is, no
neighbourhood will have a different id between files, or a different name.
In all tasks except Task 1, the dictionary argument will have both hypertension and low income
data for every neighbourhood. That is, it will be a valid CityData dictionary.
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All float values should be left as is; do not round any of them.
Using Constants
The starter code contains constants in the file constants.py that you should use in your solution for
the list indices and key identifiers for the CityData dictionary as well as the column numbers for the
input files. You may add other constants if you wish, but DO NOT place them in the file constants.py :
instead put them in the a3.py file.
Task 1: Building the data dictionary
In this task, you will write functions that read in files and build the dictionary of neighbourhood data.
You will write two functions one that adds hypertension data to a dictionary, and one that adds low
income data. You will almost certainly also need to define one or more helper functions to help you
These functions will be used to build a CityData dictionary, however the dictionary that is passed to
the functions may not yet contain all of the data.
To illustrate this, we have provided two small data files. After passing the same dictionary to both
functions with each of those small files, the dictionary should be a CityData dictionary that contains
the same information as the provided SAMPLE_DATA dictionary. Using the small hypertension file and
an empty dictionary as arguments to get_hypertension_data , the result should be that the dictionary
now contains the hypertension data as in SAMPLE_DATA , but not the low income data.
{'West Humber-Clairville':
{'id': 1, 'hypertension': [703, 13291, 3741, 9663, 3959, 5176]},
'Mount Olive-Silverstone-Jamestown':
{'id': 2, 'hypertension': [789, 12906, 3578, 8815, 2927, 3902]},
'Thistletown-Beaumond Heights':
{'id': 3, 'hypertension': [220, 3631, 1047, 2829, 1349, 1767]},
'Rexdale-Kipling':
{'id': 4, 'hypertension': [201, 3669, 1134, 3229, 1393, 1854]},
'Elms-Old Rexdale':
{'id': 5, 'hypertension': [176, 3353, 1040, 2842, 948, 1322]}}
Similarly, using the small low income file and an empty dictionary as arguments
to get_low_income_data , the result should be that the dictionary now contains the low income data as
in SAMPLE_DATA , but not the hypertension data.
{'West Humber-Clairville':
{'id': 1, 'total': 33230, 'low_income': 5950},
'Mount Olive-Silverstone-Jamestown':
{'id': 2, 'total': 32940, 'low_income': 9690},
'Thistletown-Beaumond Heights':
{'id': 3, 'total': 10365, 'low_income': 2005},
'Rexdale-Kipling':
{'id': 4, 'total': 10540, 'low_income': 2140},
'Elms-Old Rexdale':
{'id': 5, 'total': 9460, 'low_income': 2315}}
A complete CityData dictionary will have been passed to both functions. See the sample usage at
the end of the starter code file for an example of how both functions are used to build
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a CityData dictionary.
Note: While this is the first task, it is not necessarily the easiest. If you are stuck while working on this
task, we suggest moving on to other tasks and coming back to this later.
Recall that TextIO as the parameter type means the file is already open.
Function name:
(Parameter types) ->
Return type
Full Description (paraphrase to get a proper docstring description)
get_hypertension_data :
(dict, TextIO) -> None
The first parameter is a dictionary representing hypertension and/or low
income data for a neighbourhood and the second parameter is a
hypertension data file that is open for reading. This function should modify
the dictionary so that it contains the hypertension data in the file.
If a neighbourhood with data in the file is already in the dictionary then its
hypertension data should be updated. Otherwise it should be added to the
dictionary with its hypertension data.
After this function is called, the dictionary should contain key/value pairs
whose keys are the names of every neighbourhood in the hypertension data
file, and whose values are dictionaries which contain at least the
keys ID and HT for those neighbourhoods. After both
functions get_hypertension_data and get_low_income_data are called with
a dict as the first argument, this argument will be a
complete CityData type.
get_low_income_data :
(dict, TextIO) -> None
The first parameter is a dictionary representing hypertension and/or low
income data for a neighbourhood and the second parameter is a low income
data file that is open for reading. This function should modify the dictionary
so that it contains the low income data in the file.
If a neighbourhood with data in the file is already in the dictionary then its
low income data should be updated. Otherwise it should be added to the
dictionary with its low income data.
After this function is called, the dictionary should contain key/value pairs
whose keys are the names of every neighbourhood in the low income data
file, and whose values are dictionaries which contain at least the
keys ID , TOTAL , and LOW_INCOME for those neighbourhoods. After both
functions get_hypertension_data and get_low_income_data are called with
a dict as the first argument, this argument will be a
complete CityData type.
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Function name:
(Parameter types) -> Return
type
Full Description (paraphrase to get a proper docstring
description)
get_bigger_neighbourhood :
(CityData, str, str) -> str
The first parameter is a CityData dictionary, and the second and
third parameters are strings representing the names of
neighbourhoods. The function returns the name of the
neighbourhood that has a higher population, according to the low
income data.
Assume that the two neighbourhood names are different. If a
name is not in the dictionary, assume it has a population of 0. If
the two neighbourhoods are the same size, return the first name
(i.e., the leftmost one in the parameters list, not alphabetically).
get_high_hypertension_rate :
(CityData, float) ->
list[tuple[str, float]]
The first parameter is a CityData dictionary, and the second
parameter is a number between 0.0 and 1.0 (inclusive) that
represents a threshold. This function should return a list of tuples
representing all neighbourhoods with a hypertension rate greater
than or equal to the threshold. In each tuple, the first item is the
neighbourhood name and the second item is the hypertension
rate in that neighbourhood.
Compute the overall hypertension rate for a neighbourhood by
dividing the total number of people with hypertension by the total
number of adults in the neighbourhood. You may assume that no
neighbourhood has 0 population.
If this function was called with the
provided SAMPLE_DATA dictionary and a threshold of 0.3 as
arguments, then the returned value would be [('Thistletown?Beaumond Heights', 0.31797739151574084), ('Rexdale-Kipling',
0.3117001828153565)] . The order of the tuples in the list does not
matter.
get_ht_to_low_income_ratios :
(CityData) -> dict[str, float]
The parameter is a CityData dictionary. This function should
return a dictionary where the keys are the same as in the
parameter, and the values are the ratio of the hypertension rate to
the low income rate for that neighbourhood.
For the denominators for each rate, use the total number of
people as given in the corresponding data file. That is, for
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calculating the low income rate, use the total population in the
neighbourhood from the low-income data file; and for the
hypertension rate, use the sum of the total people in all three age
groups in the hypertension data. You may assume that no
neighbourhood has 0 population.
For example, if this function was called with the
provided SAMPLE_DATA dictionary as an argument, then the
returned dictionary should include the key/value pairs 'West
Humber-Clairville': 1.6683148168616895 and 'Mount Olive?Silverstone-Jamestown': 0.9676885451091314 , as well as the pairs
for the other three neighbourhoods.
You will find that writing a helper function would be useful here.
calculate_ht_rates_by_age_group :
(CityData, str) -> tuple[float,
float, float]
The first parameter is a CityData dictionary, and the second
parameter represents a neighbourhood name that is a key in the
dictionary. The function returns a tuple of three values,
representing the hypertension rate for each of the three age
groups in the neighbourhood as a percentage. (Note that this is
different from the previous two functions, where the rate was
calculated using the total numbers, and was not expressed as a
percentage.)
For example, consider the neighbourhood with the name 'Elms?Old Rexdale' in the provided SAMPLE_DATA dictionary. The rate of
hypertension for the 20-44 age group in the neighbourhood is
computed by dividing the number of people aged 20-44 with
hypertension by the total number of people aged 20-44. For this
neighbourhood, that is 176 / 3353. To get this rate as a
percentage, we then multiply by 100, for a rate of
5.24903071875932. The rate is calculated in the same way for the
45-64 and 65+ age groups. Thus, calling this function with the
provided SAMPLE_DATA dictionary and the string 'Elms-Old
Rexdale' should return (5.24903071875932, 36.593947923997185,
71.70953101361573) .
You may assume that no neighbourhood has a 0 population.
Notice that this function is used as a helper in
the get_age_standardized_ht_rate function that we have provided
for you.
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Function name:
(Parameter
types) -> Return
type
Full Description (paraphrase to get a proper docstring description)
get_correlation :
(CityData) ->
float
The parameter for this function is a CityData dictionary. This function returns the
correlation between age standardised hypertension rates and low income rates
across all neighbourhoods.
To complete this function, you will need to use the correlation function in the
module statistics . Refer to the documentation for the function to determine what
arguments to pass to the correlation function, and how to use its returned value.
You can find the documentation online here
(https://docs.python.org/3/library/statistics.html#statistics.correlation) or by
using help(statistics.correlation) . Remember that to call help on a function
from another module, you first need to import the module.
You will need to use the provided function get_age_standardized_ht_rate as a
helper to get the age-standardised rate for each neighbourhood.
Function name:
(Parameter types) ->
Return type
Full Description (paraphrase to get a proper docstring description)
order_by_ht_rate :
(CityData) ->
list[str]
The parameter is a CityData dictionary. This function will return a list of the
names of the neighbourhoods, ordered from lowest to highest age?standardised hypertension rate. We use the age-standardised rate because
we are comparing across neighbourhoods.
Assume every neighbourhood has a unique hypertension rate; i.e., that there
are no ties.
For example, if this function is called with the CityData dictionary provided in
the starter code, it will return ['Elms-Old Rexdale', 'Rexdale-Kipling',
'Thistletown-Beaumond Heights', 'West Humber-Clairville', 'Mount Olive?Silverstone-Jamestown']
There are multiple ways to solve this problem. You may choose to solve this
problem by writing your own sorting code, but you do not have to do this. You
can also use list.sort as part of your solution, if you choose.
Task 5: Required Testing ( unittest )
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Write and submit a unittest file for the get_bigger_neighbourhood function. We have provided starter
code in the test_a3.py file. We have included one test that you can use as a template to write your
other test methods. For each test method, include a brief docstring description specifying what is
being tested. Do not write examples in the docstrings. Your set of tests should all pass on correct
code, and your tests should be thorough enough that at least one of them will fail on a buggy version
of the function. There is no required number of tests; we will mark your tests by running them on the
correct code as well as several buggy versions.
code ( a3.py and test_a3.py ), the checker ( a3_checker.py together with the helper
file checker.py and folder pyta ), and two sizes of each type of data file.
Marking
These are the aspects of your work that will be marked for Assignment 3:
Correctness (70%): Your functions should perform as specified. Correctness, as measured by
our tests, will count for the largest single portion of your marks. Once your assignment is
submitted, we will run additional tests, not provided in the checker. Passing the checker does not
mean that your code will earn full marks for correctness.
Testing (15%): Your test suite will be checked by running it on incorrect/broken implementations.
Your tests should all pass on a correct version of the function, and at least one should fail on each
of our broken implementations.
Coding style (15%):
Make sure that you follow Python style guidelines
(https://q.utoronto.ca/courses/332065/pages/python-style-guide) that we have introduced and
the Python coding conventions that we have been using throughout the semester. Although we
don't provide an exhaustive list of style rules, the checker tests for style are complete, so if
your code passes the checker, then it will earn full marks for coding style with one exception:
docstrings may be evaluated separately. For each occurrence of a PyTA error, one mark (out
of 20) deduction will be applied. For example, if a C0301 (line-too-long) error occurs 3 times,
then 3 marks will be deducted.
If you encounter PyTA error R0915 (too-many-statements), that indicates that your function is
too long (more than 20 statements long). In that case, introduce helper functions to do some of
the work even if the helpers will only be called once. Your program should be broken down
into functions, both to avoid repetitive code and to make the program easier to read.
All functions, including helper functions, should have complete docstrings including
preconditions when you think they are necessary.
Also, your variable names and names of your helper functions should be meaningful. Your
code should be as simple and clear as possible.
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What to Hand In
The very last thing you do before submitting should be to run the checker program one last time.
Otherwise, you could make a small error in your final changes before submitting that causes your
code to receive zero for correctness.
Submit a3.py and test_a3.py on MarkUs by following the instructions on the course website.
Remember that spelling of filenames, including case, counts: your file must be named exactly as
above.