11 Essential Python Interview Questions

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1.) What will be the output of the code below? Explain your answer.

def extendList(val, list=[]):
   list.append(val)    
   return list

list1 = extendList(10)
list2 = extendList(123,[])
list3 = extendList('a')

print "list1 = %s" % list1
print "list2 = %s" % list2
print "list3 = %s" % list3

2.) Given a list of N numbers, use a single list comprehension to produce a new list that only contains those values that are:
(a) even numbers, and
(b) from elements in the original list that had even indicesFor example, if list[2] contains a value that is even, that value should be included in the new list, since it is also at an even index (i.e., 2) in the original list. However, if list[3] contains an even number, that number should not be included in the new list since it is at an odd index (i.e., 3) in the original list.

A simple solution to this problem would be as follows

[x for x in list[::2] if x%2 == 0]

A simple solution to this problem would be as follows

#        0   1   2   3    4    5    6    7    8
list = [ 1 , 3 , 5 , 8 , 10 , 13 , 18 , 36 , 78 ]

the list comprehension [x for x in list[::2] if x%2 == 0] will evaluate to:

[10, 18, 78]

The expression works by first taking the numbers that are at the even indices, and then filtering out all the odd numbers.

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