CMSI 386: Programming Languages: Homework #1

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1. Write a Python function that accepts a number of U.S. cents and returns a tuple containing, respectively, the
smallest number of U.S. quarters, dimes, nickels, and pennies that equal the given amount. Use the Python
divmod built-in function.
>>> change(96)
(3, 2, 0, 1)
>>> change(8)
(0, 0, 1, 3)
2. Write a Python function that takes in a string s and returns the string which is equivalent to s but with all
ASCII vowels removed. For example:
>>> strip_vowels(“Hello, world”)
“Hll, wrld”
3. Write a Python function that randomly permutes a string. By random we mean that each time you call the
function for a given argument all possible permutations are equally likely (note that “random” is not the same
as “arbitrary.”) For example:
>>> scramble(“Hello, world”)
“w,dlroH elol”
4. Write a Python generator function that yields powers of two starting at 1 and going up to some limit. For
example:
>>> for x in powers_of_two(70): print x
1
2
4
8
16
32
64
5. Write a Python generator function that yields powers of an arbitrary base starting at exponent 0 and going up
to some limit. For example:
>>> for x in powers(3, 400): print x
1/30/2014 CMSI 386: Programming Languages: Homework #1
http://cs.lmu.edu/~ray/classes/pl/assignment/1/ 2/3
1
3
9
27
81
243
6. Write a function that interleaves two lists. If the lists do not have the same length, the elements of the longer
list should end up at the end of the result list. For example:
>>> interleave([“a”, “b”], [1, 2, True, None])
[“a”, 1, “b”, 2, True, None]
7. Write a function that doubles up each item in an list. For example:
>>> stutter([5,4,[3],9])
[5,5,4,4,[3],[3],9,9]
8. Write a Python script (in the file prefixes.py) that writes successive prefixes of its first input argument, one
per line, starting with the first prefix, which is zero characters long. For example:
$ python prefixes.py vanrossum
v
va
van
vanr
vanro
vanros
vanross
vanrossu
vanrossum
9. Write a Python script (in the file lines.py) that reports the number of non-blank, non-fully-commented lines in
the file named by the first argument. Blank lines are those that have either no characters or consist entirely
of whitespace; commented lines are those whose first non-whitespace character is #. For example, if the file
states.txt has 50 non-blank, non-comment lines:
$ python lines.py states.txt
50
10. Flesh out the unit test file for problems 1-7 that I have started here for you. (Note that you do not need to
submit unit tests for problems 8 and 9.) You will be graded on how well you cover each of your functions —
think zeros, negatives, extremely large numbers, etc.
frompythonwarmupimport(change,strip_vowels,scramble,powers_of_two,powers,
interleave,stutter)
importunittest
defanagram(s,t):
returnsorted(s)==sorted(t)
classPythonWarmupTestCase(unittest.TestCase):
deftest_change(self):
1/30/2014 CMSI 386: Programming Languages: Homework #1
http://cs.lmu.edu/~ray/classes/pl/assignment/1/ 3/3
self.assertEqual((3,2,0,2),change(97))
self.assertEqual((0,0,1,3),change(8))
self.assertEqual((10,0,0,0),change(250))
#Moretests
deftest_strip_vowels(self):
self.assertEqual(‘Hll,wrld’,strip_vowels(“Hello,world”))
#Moretests
deftest_scramble(self):
data=[“”,”a”,”rat”,”BSOD”,”BDFL”,”Pythontesting”]
forsindata:
self.assertTrue(anagram(s,scramble(s)))
#test_powers_of_twogoeshere
#test_powersgoeshere
#test_interleavegoeshere
#test_stuttergoeshere
if__name__==’__main__’:
unittest.main()