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interlacing strings in python


I had a question for a test where I had to interlace letters from two strings into one, I did it using the following code:

'abcd' and 'efghi' -> 'aebfcgdhi'

s1,s2='abcd' ,'efghi'
t=[a+b for a,b in zip(s1, s2) ]
ls1 = len(s1)
ls2 = len(s2)
if ls1 > ls2:
    t.extend(s1[ls2:])
elif ls1 < ls2:
    t.extend(s2[ls1:])
print ''.join(t)

I first tried using the following which seems to work only when strings are the same length or s2 is the longer string.

 print  ''.join([a+b for a,b in zip(s1, s2)]) + max(s1,s2)[min(len(s1),len(s2)):]

Where did I go wrong in my logic?


Solution

  • To make your code work, you just need to use the key param in the max function

    print  ''.join([a+b for a,b in zip(s1, s2)]) + max(s1,s2, key=len)[min(len(s1),len(s2)):]
    

    Alternatively, you can use itertools.izip_longest to iterate till the biggest of the two iterables is exhausted. So, this solution works irrespective of the lengths of strings.

    import itertools
    s1,s2='abcd' ,'efghi'
    print "".join(y for x in itertools.izip_longest(s1, s2) for y in x if y)
    

    Output

    aebfcgdhi
    

    Edit:

    Without using itertools

    s1,s2='abcd' ,'efghi'
    minLen = min(len(s1), len(s2))
    print "".join(y for x in zip(s1, s2) for y in x) + s1[minLen:] + s2[minLen:]