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first commit - added practice files for first class
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‎basic/alice.txt‎

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‎basic/list1.py‎

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# Basic list exercises
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# Fill in the code for the functions below. main() is already set up
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# to call the functions with a few different inputs,
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# printing 'OK' when each function is correct.
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# The starter code for each function includes a 'return'
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# which is just a placeholder for your code.
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# It's ok if you do not complete all the functions, and there
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# are some additional functions to try in list2.py.
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# A. match_ends
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# Given a list of strings, return the count of the number of
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# strings where the string length is 2 or more and the first
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# and last chars of the string are the same.
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# Note: python does not have a ++ operator, but += works.
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def match_ends(words):
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# +++your code here+++
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return
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# B. front_x
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# Given a list of strings, return a list with the strings
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# in sorted order, except group all the strings that begin with 'x' first.
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# e.g. ['mix', 'xyz', 'apple', 'xanadu', 'aardvark'] yields
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# ['xanadu', 'xyz', 'aardvark', 'apple', 'mix']
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# Hint: this can be done by making 2 lists and sorting each of them
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# before combining them.
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def front_x(words):
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# +++your code here+++
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return
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# C. sort_last
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# Given a list of non-empty tuples, return a list sorted in increasing
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# order by the last element in each tuple.
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# e.g. [(1, 7), (1, 3), (3, 4, 5), (2, 2)] yields
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# [(2, 2), (1, 3), (3, 4, 5), (1, 7)]
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# Hint: use a custom key= function to extract the last element form each tuple.
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def sort_last(tuples):
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# +++your code here+++
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return
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# Simple provided test() function used in main() to print
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# what each function returns vs. what it's supposed to return.
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def test(got, expected):
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if got == expected:
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prefix = ' OK '
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else:
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prefix = ' X '
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print('{} got: {} expected: {}'.format(prefix, repr(got), repr(expected)))
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# Calls the above functions with interesting inputs.
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def main():
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print('match_ends')
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test(match_ends(['aba', 'xyz', 'aa', 'x', 'bbb']), 3)
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test(match_ends(['', 'x', 'xy', 'xyx', 'xx']), 2)
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test(match_ends(['aaa', 'be', 'abc', 'hello']), 1)
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print()
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print('front_x')
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test(front_x(['bbb', 'ccc', 'axx', 'xzz', 'xaa']),
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['xaa', 'xzz', 'axx', 'bbb', 'ccc'])
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test(front_x(['ccc', 'bbb', 'aaa', 'xcc', 'xaa']),
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['xaa', 'xcc', 'aaa', 'bbb', 'ccc'])
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test(front_x(['mix', 'xyz', 'apple', 'xanadu', 'aardvark']),
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['xanadu', 'xyz', 'aardvark', 'apple', 'mix'])
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print()
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print('sort_last')
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test(sort_last([(1, 3), (3, 2), (2, 1)]),
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[(2, 1), (3, 2), (1, 3)])
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test(sort_last([(2, 3), (1, 2), (3, 1)]),
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[(3, 1), (1, 2), (2, 3)])
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test(sort_last([(1, 7), (1, 3), (3, 4, 5), (2, 2)]),
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[(2, 2), (1, 3), (3, 4, 5), (1, 7)])
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if __name__ == '__main__':
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main()

‎basic/list2.py‎

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# Additional basic list exercises
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# D. Given a list of numbers, return a list where
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# all adjacent == elements have been reduced to a single element,
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# so [1, 2, 2, 3] returns [1, 2, 3]. You may create a new list or
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# modify the passed in list.
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def remove_adjacent(nums):
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# +++your code here+++
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return
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# E. Given two lists sorted in increasing order, create and return a merged
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# list of all the elements in sorted order. You may modify the passed in lists.
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# Ideally, the solution should work in "linear" time, making a single
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# pass of both lists.
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def linear_merge(list1, list2):
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# +++your code here+++
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return
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# Note: the solution above is kind of cute, but unforunately list.pop(0)
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# is not constant time with the standard python list implementation, so
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# the above is not strictly linear time.
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# An alternate approach uses pop(-1) to remove the endmost elements
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# from each list, building a solution list which is backwards.
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# Then use reversed() to put the result back in the correct order. That
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# solution works in linear time, but is more ugly.
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# Simple provided test() function used in main() to print
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# what each function returns vs. what it's supposed to return.
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def test(got, expected):
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if got == expected:
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prefix = ' OK '
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else:
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prefix = ' X '
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print('{} got: {} expected: {}'.format(prefix, repr(got), repr(expected)))
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# Calls the above functions with interesting inputs.
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def main():
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print('remove_adjacent')
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test(remove_adjacent([1, 2, 2, 3]), [1, 2, 3])
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test(remove_adjacent([2, 2, 3, 3, 3]), [2, 3])
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test(remove_adjacent([]), [])
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print()
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print('linear_merge')
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test(linear_merge(['aa', 'xx', 'zz'], ['bb', 'cc']),
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['aa', 'bb', 'cc', 'xx', 'zz'])
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test(linear_merge(['aa', 'xx'], ['bb', 'cc', 'zz']),
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['aa', 'bb', 'cc', 'xx', 'zz'])
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test(linear_merge(['aa', 'aa'], ['aa', 'bb', 'bb']),
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['aa', 'aa', 'aa', 'bb', 'bb'])
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if __name__ == '__main__':
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main()

‎basic/mimic.py‎

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"""Mimic pyquick exercise -- optional extra exercise.
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Read in the file specified on the command line.
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Do a simple split() on whitespace to obtain all the words in the file.
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Rather than read the file line by line, it's easier to read
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it into one giant string and split it once.
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Build a "mimic" dict that maps each word that appears in the file
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to a list of all the words that immediately follow that word in the file.
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The list of words can be be in any order and should include
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duplicates. So for example the key "and" might have the list
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["then", "best", "then", "after", ...] listing
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all the words which came after "and" in the text.
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We'll say that the empty string is what comes before
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the first word in the file.
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With the mimic dict, it's fairly easy to emit random
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text that mimics the original. Print a word, then look
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up what words might come next and pick one at random as
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the next work.
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Use the empty string as the first word to prime things.
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If we ever get stuck with a word that is not in the dict,
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go back to the empty string to keep things moving.
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Note: the standard python module 'random' includes a
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random.choice(list) method which picks a random element
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from a non-empty list.
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For fun, feed your program to itself as input.
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Could work on getting it to put in linebreaks around 70
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columns, so the output looks better.
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"""
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import random
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import sys
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def mimic_dict(filename):
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"""Returns mimic dict mapping each word to list of words which follow it."""
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# +++your code here+++
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return
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def print_mimic(mimic_dict, word):
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"""Given mimic dict and start word, prints 200 random words."""
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# +++your code here+++
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return
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# Provided main(), calls mimic_dict() and mimic()
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def main():
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if len(sys.argv) != 2:
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print('usage: ./mimic.py file-to-read')
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sys.exit(1)
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dict = mimic_dict(sys.argv[1])
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print_mimic(dict, '')
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if __name__ == '__main__':
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main()

‎basic/small.txt‎

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We are not what we should be
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We are not what we need to be
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But at least we are not what we used to be
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-- Football Coach
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‎basic/solution/list1.py‎

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# Basic list exercises
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# Fill in the code for the functions below. main() is already set up
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# to call the functions with a few different inputs,
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# printing 'OK' when each function is correct.
5+
# The starter code for each function includes a 'return'
6+
# which is just a placeholder for your code.
7+
# It's ok if you do not complete all the functions, and there
8+
# are some additional functions to try in list2.py.
9+
10+
# A. match_ends
11+
# Given a list of strings, return the count of the number of
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# strings where the string length is 2 or more and the first
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# and last chars of the string are the same.
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# Note: python does not have a ++ operator, but += works.
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def match_ends(words):
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# +++your code here+++
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# LAB(begin solution)
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count = 0
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for word in words:
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if len(word) >= 2 and word[0] == word[-1]:
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count = count + 1
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return count
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# LAB(replace solution)
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# return
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# LAB(end solution)
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# B. front_x
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# Given a list of strings, return a list with the strings
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# in sorted order, except group all the strings that begin with 'x' first.
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# e.g. ['mix', 'xyz', 'apple', 'xanadu', 'aardvark'] yields
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# ['xanadu', 'xyz', 'aardvark', 'apple', 'mix']
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# Hint: this can be done by making 2 lists and sorting each of them
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# before combining them.
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def front_x(words):
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# +++your code here+++
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# LAB(begin solution)
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# Put each word into the x_list or the other_list.
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x_list = []
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other_list = []
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for w in words:
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if w.startswith('x'):
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x_list.append(w)
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else:
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other_list.append(w)
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return sorted(x_list) + sorted(other_list)
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# LAB(replace solution)
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# return
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# LAB(end solution)
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# LAB(begin solution)
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# Extract the last element from a tuple -- used for custom sorting below.
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def last(a):
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return a[-1]
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# LAB(end solution)
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# C. sort_last
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# Given a list of non-empty tuples, return a list sorted in increasing
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# order by the last element in each tuple.
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# e.g. [(1, 7), (1, 3), (3, 4, 5), (2, 2)] yields
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# [(2, 2), (1, 3), (3, 4, 5), (1, 7)]
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# Hint: use a custom key= function to extract the last element form each tuple.
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def sort_last(tuples):
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# +++your code here+++
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# LAB(begin solution)
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return sorted(tuples, key=last)
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# LAB(replace solution)
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# return
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# LAB(end solution)
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# Simple provided test() function used in main() to print
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# what each function returns vs. what it's supposed to return.
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def test(got, expected):
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if got == expected:
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prefix = ' OK '
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else:
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prefix = ' X '
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print('{} got: {} expected: {}'.format(prefix, repr(got), repr(expected)))
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# Calls the above functions with interesting inputs.
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def main():
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print('match_ends')
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test(match_ends(['aba', 'xyz', 'aa', 'x', 'bbb']), 3)
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test(match_ends(['', 'x', 'xy', 'xyx', 'xx']), 2)
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test(match_ends(['aaa', 'be', 'abc', 'hello']), 1)
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print()
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print('front_x')
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test(front_x(['bbb', 'ccc', 'axx', 'xzz', 'xaa']),
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['xaa', 'xzz', 'axx', 'bbb', 'ccc'])
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test(front_x(['ccc', 'bbb', 'aaa', 'xcc', 'xaa']),
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['xaa', 'xcc', 'aaa', 'bbb', 'ccc'])
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test(front_x(['mix', 'xyz', 'apple', 'xanadu', 'aardvark']),
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['xanadu', 'xyz', 'aardvark', 'apple', 'mix'])
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print()
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print('sort_last')
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test(sort_last([(1, 3), (3, 2), (2, 1)]),
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[(2, 1), (3, 2), (1, 3)])
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test(sort_last([(2, 3), (1, 2), (3, 1)]),
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[(3, 1), (1, 2), (2, 3)])
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test(sort_last([(1, 7), (1, 3), (3, 4, 5), (2, 2)]),
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[(2, 2), (1, 3), (3, 4, 5), (1, 7)])
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if __name__ == '__main__':
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main()

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