Week 3: Structured Types 5. Tuples and Lists Exercise: odd tuples

ESTIMATED TIME TO COMPLETE: 5 minutes

Write a procedure called oddTuples, which takes a tuple as input, and returns a new tuple as output, where every other element of the input tuple is copied, starting with the first one. So if test is the tuple (‘I‘, ‘am‘, ‘a‘, ‘test‘, ‘tuple‘), then evaluating oddTuples on this input would return the tuple (‘I‘, ‘a‘, ‘tuple‘). 

def oddTuples(aTup):
　　‘‘‘
　　aTup: a tuple

　　returns: tuple, every other element of aTup.
　　‘‘‘
　　# Your Code Here
　　return aTup[::2]

一开始写错成return oddTuples[::2] 这样子报错：TypeError: ‘function‘ object is not subscriptable。 注意，我们要分隔的是aTup这个元祖，不是oddTuples这个函数。

答案二：

def oddTuples(aTup):
    ‘‘‘
    aTup: a tuple
    
    returns: tuple, every other element of aTup. 
    ‘‘‘
    # a placeholder to gather our response
    rTup = ()
    index = 0

    # Idea: Iterate over the elements in aTup, counting by 2
    #  (every other element) and adding that element to 
    #  the result
    while index < len(aTup):
        rTup += (aTup[index],)
        index += 2

    return rTup