Compsci 101, Fall 2012, October 29

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    Dictionary Basics

    In a Python console the following appears illustrating some of the methods that work with dictionaries, in particular there's a variable d that stores a dictionary as shown. What the user types is shown in italics. 
    >> d
{'duke': 50, 'columbia': 30, 'stanford': 20}
>>> d.keys()
['duke', 'columbia', 'stanford']
>>> d.values()
[50, 30, 20]
>>> d.items()
[('duke', 50), ('columbia', 30), ('stanford', 20)]
>>> [x[1] for x in d.items()]
[50, 30, 20]
    1. If the x[1] in the last line is replaced by x[0] what is printed?

      1. [20, 30, 50]

      2. ['duke', 'duke', 'duke']

      3. ['duke', 'columbia', 'stanford']

    2. After the user types d['duke'] = 80, what is printed by the expression d.values()?

      1. [50, 30, 20]

      2. [80, 30, 20]

      3. [50, 80, 30]

    3. The code below is executed next (after the value associated with 'duke' is changed to 80), what is printed? 
      for name in d:
    d[name] += 10
print d

      1. {'duke': 90, 'columbia': 40, 'stanford': 30}

      2. {'duke': 90, 'columbia': 30, 'stanford': 20}

      3. {'duke': 90, 'columbia': 40, 'stanford': 20}

      Jotto Stuff

    4. In the Jotto Assignment the function process_common_last is supposed to remove all words from the global variable _possiblewords that do not have common letters in common with the last word guessed by the computer player. A student suggests this code: for w in _possiblewords: if commonCount(w,_lastguess) != common: _possiblewords.remove(w) Which of the following is the best characterization of this code:

      1. It is not correct syntactically because either there is no remove method for lists or because the != operator is not defined.

      2. It expresses the right idea, but because a word is removed from a list during the loop/iteration over the list it is likely that the resulting list will contain words that should have been removed, but were not.

      3. The code works correctly.

    5. Suppose a list is created in process_common_last as follows: bw = [w for w in _possiblewords if commonCount(w,_lastguess) != common]

      Which one(s) of the following will change _possiblewords correctly (more than one is possible)?

      1. _possiblewords = list(set(_possiblewords) - set(bw))

      2. _possiblewords = [w for w in _possiblewords if not w in bw]

      3. _possiblewords = list(set(_possiblewords) & set(bw))