CPE 202
Lab 1: Python Classes, Recursion, and Testing!
Part 1
1. Review the code in location.py. Note that there is a class definition for a Location class, and an associated
__init__ method. In addition, there is code to create Location objects and print information associated with
those objects.
class Location:
def __init__(self, name, lat, long):
self.name = name # string for name of location
self.lat = lat # latitude in degrees (-90 to 90)
self.long = long # longitude in degrees (-180 to 180)
2. Without modifying the code, run location.py in whatever environment you wish (again, reference the Getting
Started document if you need help in doing this)
3. Note the information that is printed out for each Location object – you should see something like this:
Location 1: <__main__.Location object at 0x000001F6A2E0C7B8>
4. Since we haven’t provided any specific method to provide a representation for the class, Python uses a
default method. What do you notice about the information for loc1 and loc4 ?
5. Also note the result of the equal comparisons between the locations, in particular loc1==loc3 and loc1==loc4.
Make sure you understand why the results are what they are.
6. Now modify the location.py code, adding in the methods (__eq__() and __repr__()). See the
location_tests.py to figure out what the repr method should look like. You can also use the boilerplate generator
as shown in class – you can find the link in PolyLearn.
7. Run the location.py code with the modifications made above.
8. Now review the information printed out for each location. The __repr__ method of Location is now being
used when printing the object.
9. Examine the results of the equal comparisons. How are they different from before the __eq__ method was
added?
10. Now that __eq__ and __repr__ functions have been added to the Location class, execute the
location_tests.py file and observe the results. Add additional tests that will test the __init__, __eq__ and
__repr__ functions.
11. Unload your updated location.py and location_tests.py files to Canvas for this part of the lab, and make
sure you understand what the above questions are driving at, and if you have any uncertainties, ask! We’ll also
go over the answers later during lecture or lab time.
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CPE 202 Winter 2022
Part 2
1. In the lab1.py file, complete the iterative function to find the maximum integer in a list of integers.
def max_list_iter(int_list): # must use iteration not recursion “””finds
the max of a list of numbers and returns the value (not the index) If
int_list is empty, returns None. If list is None, raises ValueError”””
2. In the lab1.py file, complete the recursive function to reverse a list of integers:
def reverse_rec(int_list): # must use recursion
“””recursively reverses a list of numbers and returns the reversed list
If list is None, raises ValueError”””
3. In the lab1.py file, complete the recursive function to search a list of integers using binary search along with
test cases. If the target of the search is in the list, the function returns its index.
def bin_search(target, low, high , int_list): # must use recursion
“””searches for target in int_list[low..high] and returns index if found
If target is not found returns None. If list is None, raises ValueError
“””
Test Cases
Many people tend to focus on writing code as the singular activity of a programmer, but testing is one of the
most important tasks that one can perform while programming. Proper testing provides a degree of confidence
in your solution. Systematic testing helps you to discover and then debug your code. Writing high quality test
cases can greatly simplify the tasks of both finding and fixing bugs and, as such, will save you time during
development. However, testing does not guarantee that your program is correct.
For this part of the lab you will practice writing some simple test cases to gain experience with
the unittest framework. I recommend watching the first 20 minutes or so of the following video if you need
more guidance on testing in Python. https://www.youtube.com/watch?v=6tNS–WetLI
Using your editor/IDE of choice, open the lab1_test_cases.py file. This file defines, using code that we will treat
as a boilerplate for now, a testing class with a single testing function.
In the test_expressions function you will see some test cases already provided. You must add additional test
cases to verify that your functions (max_list_iter, reverse_rec, bin_search) are correct.
Submission/Grading
Ensure that the following file have been submitted to Canvas by the due date:
• location.py o Updated per the instructions in Part 1
• location_tests.py o Comprehensive test cases as described in Part 1
• lab1.py o Correct and well documented iterative max_list_iter, recursive reverse_rec, and recursive
bin_search functions based on the template provided
• lab1_test_cases.py A complete set of test cases for the functions above. Your test cases should test
boundary conditions and other possible errors based on the structure of your program. For each test provide a
comment (or docstring) that explains what it is testing. Your tests cases will be tested with known incorrect
(buggy) versions of the functions in lab1.py and will also be tested for 100% code coverage.
.
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