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Python

Posted by Jason Chiu
Jason Chiu
4,373 Points

Extra Credit for Python Slice

Hi all,

How can I blend two different lists together using only the slice technique, as what was told to do in extra credit section of slicing?

1 Answer

Chris Freeman
MOD
Chris Freeman
Treehouse Moderator 68,468 Points
Chris Freeman
Chris Freeman
Treehouse Moderator 68,468 Points

One solution is to walk down both lists and append each item to a results lists. The issue is how to handle the case where the two lists have different lengths. Using a simple index notation "[n]" will eventually raise an IndexError on the shorter list.

The nice feature of using slices is you are protected from indexing issues because the Alec returns an empty list of the index is it found.

For example:

# define s list
a =[1,2,3,4]
# get index 3 and 4
a[3]  # 4
a[4]  # raises error

# using slices
a[3:3]  # [4]
a[4:4]  # []

Using slices to crest a merge function:

def merge(a,b):
    maxlen = max(len(a), len(b))
    result = []
    for idx in range(maxlen):
        result.extend(a[idx:idx+1])
        result.extend(b[idx:idx+1])
    return result

a =[1,2,3,4]
b=['a', 'b', 'c', 'd', 'e', 'f']
print(merge(a,b))

# creates
[1, 'a', 2, 'b', 3, 'c', 4, 'd', 'e', 'f']