Question

Sorry for the very basic question, but this is actually a 2-part question:

1. Given a list, I need to replace the values of ‘?’ with ‘i’ and the ‘x’ with an integer, 10. The list does not always have the same number of elements, so I need a loop that permits me to do this.

   a = ['1', '7', '?', '8', '5', 'x']
   

2. How do I grab the index of where the value is equal to ‘?’. It’d be nice if this show me how I could grab all the index and values in a list as well.

Answer 1

Write a function for it and use map() to call it on every element:

def _replaceitem(x):
    if x == '?':
        return 'i'
    elif x == 'x':
       return 10
    else:
        return x

a = map(_replaceitem, a)

Note that this creates a new list. If the list is too big or you don’t want this for some other reason, you can use for i in xrange(len(a)): and then update a[i] if necessary.

To get (index, value) pairs from a list, use enumerate(a) which returns an iterator yielding such pairs.

To get the first index where the list contains a given value, use a.index('?').