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BBM 103: Introduction to Programming Laboratory I
Quiz 5
Subject: Handling Exceptions: Try Not to Go BOOM
Problem Definition
Given the values div, nondiv, from, and to, you are expected to write a Python program
which finds the numbers between from and to (both included) that are divisible by div but
are not a multiple of nondiv, and then compares the obtained result with a list of numbers
given for comparison.
Example:
For div = 2, nondiv = 4, from = 20, to = 32, and comparison data = 22 26 30
the result should be: 22 26 30 with a perfect match to the comparison data.
Simple enough, right? Or is it?
Ask yourself: what could possibly go wrong with your program? As a matter of fact, lots
of things could go wrong (e.g. what if div or nondiv is 0? What if operands are given
as something other than a number?), so let’s make the problem definition a little bit more
specific: Write the Python program described above so that your program won’t
go KABOOM no matter what happens with the input.
Expected Exception Handling
Your program should operate on two input text files:
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BBM 103: Introduction to Programming Laboratory I
• sys.argv[1] - will provide you the input operands in the following (expected!) format:
div < space > nondiv < space > from < space > to
Here, each line of the file should be processed separately, (as each line will contain a set
of different operands).
• sys.argv[2] - will provide you the data for comparison (each line of this file should be
matched to the results of processing the corresponding input line in the first input file).
Hence, your program will expect to be run using the following command (assuming the input
file names are operands.txt and comparison data.txt respectively):
python3 quiz5.py operands.txt comparison data.txt
IndexError - For the Missing Expected Command-Line Arguments
The first problem that can occur is if the number of command-line arguments is less then
expected. Assume that your code is executed using the following command:
python3 quiz5.py operands.txt
Clearly, one of the expected arguments is missing, and trying to access sys.argv[2] will raise
an IndexError exception. Your code must handle the problem of insufficient command-line
arguments by printing the error message ”IndexError: number of input files less than
expected.”.
IOError
Another problem can occur in case the input files are not reachable at the specified file path
(if files do not exist, or if their names are misspelled, etc.). Assume that your code is executed
using the following command (and that somefile.txt does not exist):
python3 quiz5.py operands.txt somefile.txt
Your code must handle the resulting IOError exception by printing the error message: ”IOError:
cannot open somefile.txt”. Note that the file name which caused the exception must be
stated in the error message.
Exception Handling Upon Successful Opening of the Input Files
If the input files are opened successfully, your code should proceed to perform the necessary
calculations. The steps you should take are as follows:
• Read a line with the given operands from the first input file.
• Calculate the resulting list of numbers.
• Compare your result to the given comparison data in the second input file (by reading
it from the corresponding line; i.e. the results obtained using the operands from the
first line in the first input file should be compared to the data given in the first line of
the second input file, etc.).
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BBM 103: Introduction to Programming Laboratory I
• Repeat these steps for each line of input.
In order to make your program robust against any possible errors that may arise during performing these steps, you are expected to incorporate the following exception handling:
ValueError
If any of the operands are given as non-numeric values, trying to convert them to integers
will raise a ValueError exception. Your code must handle this problem by printing the error
message ”ValueError: only numeric input is accepted.”, and the given input which
caused the trouble (see I/O samples for the expected output format).
IndexError
If the number of operands is less than expected, trying to access them from the list of operands
will raise an IndexError exception. Your code must handle this problem by printing the error
message ”IndexError: number of operands less than expected.”, and the given input
which caused the trouble (see I/O samples for the expected output format).
ZeroDivisionError
If any one of div or nondiv operands is given as 0, a ZeroDivisionError exception will be
raised while performing the calculations. Your code must handle this problem by printing the
error message ”ZeroDivisionError: You can’t divide by 0.”, and the given input which
caused the trouble (see I/O samples for the expected output format).
AssertionError
If everything goes well and you get a result for a set of operands, you will need to assert that
your result matches the given comparison data. In case they do not match, your code should
raise an AssertionError exception and handle it by printing your result, the given comparison
data, and the error message ”Assertion Error: results don’t match.” (see I/O samples
for the expected output format).
Any Other Exception
Just in case, you should be prepared for any other possible problem that can occur when your
code is run, as we cannot always anticipate all future problems. In case of any other error
not mentioned above, your code should print the error message ”kaBOOM: run for your
life!”.
What If All Goes Well?
If all goes well and your result matches the given comparison data, your program should
print your result, the given comparison data, and the following message: ”Goool!!!” (see
I/O samples for the expected output format).
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BBM 103: Introduction to Programming Laboratory I
Terminating Your Program
In order to prove that your code didn’t blow up on any given input, your program should
print the message: ”˜Game Over ˜” just before it exits. This should be handled in a finally
block.
Notes
• Do not miss the submission deadline.
• Save all your work until the quiz is graded.
• You can ask your questions via Piazza and you are supposed to be aware of everything
discussed on Piazza.
• You must submit your work with the file hierarchy as stated below:
→ <quiz5.py>
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BBM 103: Introduction to Programming Laboratory I
Sample Inputs and Expected Outputs
Consider the following input files:
operands.txt: comparison_data.txt
---------------- ----------------------
2 4 20 32 22 26 30
2 4 20 32 22 26
4 20 32 thisgonnagoboom
0 4 20 32 22 26 30 thisgonnablow
2 tuzak 20 pusu thisgonnablowtoo
3 6 20 32 21 27
3.2 6 20 32 21 27
3 6 25.5 32 21 27
---------------- ----------------------
Run 1:
python3 quiz5.py operands.txt comparison data.txt
The expected output:
------------
My results: 22 26 30
Results to compare: 22 26 30
Goool!!!
------------
My results: 22 26 30
Results to compare: 22 26
AssertionError: results don’t match.
------------
IndexError: number of operands less than expected.
Given input: 4 20 32
------------
ZeroDivisionError: You can’t divide by 0.
Given input: 0 4 20 32
------------
ValueError: only numeric input is accepted.
Given input: 2 tuzak 20 pusu
------------
My results: 21 27
Results to compare: 21 27
Goool!!!
------------
My results: 21 27
Results to compare: 21 27
Goool!!!
------------
My results: 27
Results to compare: 21 27
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BBM 103: Introduction to Programming Laboratory I
AssertionError: results don’t match.
˜ Game Over ˜
Run 2:
python3 quiz5.py operands.txt
The expected output:
IndexError: number of input files less than expected.
˜ Game Over ˜
Run 3:
python3 quiz5.py operands.txt nonexistentfile.txt
The expected output:
IOError: cannot open nonexistentfile.txt
˜ Game Over ˜
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