On 06Aug2015 16:55, Quiles, Stephanie <stephanie.quiles...@albright.edu> wrote:
I need to do the following assignment. I need to know how do i hard code an
example for each of the operators I am implementing? What i have so far is
below? He said he does not care if we plug in some numbers or if we have user
input numbers, however I am unsure of how to write a program that tests each
operator? Or can i write one that tests all of them? I don’t know where to
start with this. Please help!
For someone who doesn't know where to start, you seem to have a lot of decent
looking code. Is the code below all yours? If so, a good start.
Also, please try to preserve the indentation when pasting in code; indentation
is critical in Python as you know and incorrect indentation, when not an
outright syntax error, can be a source of bugs. I'll presume your code was
originally indented correctly.
Note that in this list we _do_ like code to be pasted inline where it can be
seen directly and commented on like any other part of the message text. We're
not big on attachments or links to external things (other than doco citations
like your reference to the operators Python page).
You may implement as many of these operators as you like (such as isub,
itruediv, etc.) You MUST indicate in your header information which operators
you are implementing, and you MUST hard code an example for each.
"Header information" is usually an opening comment. So perhaps start the
program with text like this:
# Here is a Fraction class implementing variaous operators. It currently
# supports:
#
# + (addition)
# - (subtraction)
# * (multiplication)
# / (true division)
#
and so forth.
Regarding examples and tests, one workable approach to to make your program
work as a "main program". The idea is that is invoked as a main program it will
run the examples or tests.
As your code sits now it could be used as a module - someone could place it
into python's library tree and import it, and use your Fraction class.
However, you can of course run it directly at the command prompt, eg:
% python your-fraction-file.py
When you do that, the code is still imported as a module but with the special
name '__main__'. So what a lot of python modules do is have a "main" function
which is to be fired only in the command line circumstance, such as:
def main():
F1 = Fraction(1, 2) # 1/2
F2 = Fraction(2, 3) # 2/3
print("F1 =", F1)
print("F2 =", F2)
print("F1 + F2 =", F1 + F2)
print("F1 - F2 =", F1 - F2)
print("F1 * F2 =", F1 * F2)
In order to make your program work as both an importable module which defines
the Fraction class but does not run the main function and also as a main
program which defines the class and then runs the main function you put this
piece of boilerplate code on the very bottom of the program:
if __name__ == '__main__':
main()
which checks if you're invoking it directly from the command line. If so, run
the main function.
Hopefully that gives you an idea about hardwiring examples also.
Regarding tests, you might write a simple function like this:
def check(label, computed, expected):
ok = computed == expected
if ok:
print(label, 'OK', computed, '==', expected)
else:
print(label, 'BAD', computed, '!=', expected)
return ok
Then you might consider modifying your main program to run tests instead of
bare examples, replacing:
print("F1 + F2 =", F1 + F2)
with:
check("F1 + F2", F1 + F2, Fraction(7, 6))
Because check() returns whther the check was ok, you might even count the
number of failures for some kind of report:
fail_count = 0
...
if not check("F1 + F2", F1 + F2, Fraction(7, 6)):
fail_count += 1
... more checks ...
print(fail_count, "failures")
and so forth.
This also gets you test code so that you can test your own program for
correctness before submitting your assignment.
Feel free to return to this list with updated code and new questions.
Cheers,
Cameron Simpson <c...@zip.com.au>
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