Is there a pythonic way to insert an element into every 2nd element in a string?
I have a string: ‘aabbccdd’ and I want the end result to be ‘aa-bb-cc-dd’.
I am not sure how I would go about doing that.
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Answer
Assume the string’s length is always an even number,
>>> s = '12345678'>>> t = iter(s)>>> '-'.join(a+b for a,b in zip(t, t))'12-34-56-78'The t can also be eliminated with
>>> '-'.join(a+b for a,b in zip(s[::2], s[1::2]))'12-34-56-78'The algorithm is to group the string into pairs, then join them with the - character.
The code is written like this. Firstly, it is split into odd digits and even digits.
>>> s[::2], s[1::2]('1357', '2468')Then the zip function is used to combine them into an iterable of tuples.
>>> list( zip(s[::2], s[1::2]) )[('1', '2'), ('3', '4'), ('5', '6'), ('7', '8')]But tuples aren’t what we want. This should be a list of strings. This is the purpose of the list comprehension
>>> [a+b for a,b in zip(s[::2], s[1::2])]['12', '34', '56', '78']Finally we use str.join() to combine the list.
>>> '-'.join(a+b for a,b in zip(s[::2], s[1::2]))'12-34-56-78'The first piece of code is the same idea, but consumes less memory if the string is long.