Dynamically slice a string using a variable

Question

I am trying to slice a string and insert the components into a list (or index, or set, or anything), then compare them, such that

Input:

abba

Output:

['ab', 'ba']

Given a variable length of the input.

So if I slice a string

word = raw_input("Input word"
slicelength = len(word)/2
longword[:slicelength]

such that

    list = [longwordleftslice]
    list2 = [longwordrightslice]

    list2 = list2[::-1 ] ## reverse slice
    listoverall = list + list2

However, the built-in slice command [:i] specifies that i be an integer.

What can I do?

wim · Accepted Answer · 2014-01-25 15:34:10Z

1

You can always do that..

word = "spamspamspam"
first_half = word[:len(word)//2]
second_half = word[len(word)//2:]

For any string s and any integer i, s == s[:i] + [:i] is invariant. Note that if len(word) is odd, you will get one more character in the second "half" than the first.

If you are using python 3, use input as opposed to raw_input.

edited Jan 25, 2014 at 15:34

answered Feb 22, 2012 at 4:14

wim

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Comments

senderle · Accepted Answer · 2012-02-22 04:20:46Z

1

I'm guessing you're using Python 3. Use // instead of /. In Python 3, / always returns a float, which lists don't like. // returns an int, truncating everything past the decimal point.

Then all you have to do is slice before and after the midpoint.

>>> a = [0, 1, 2, 3, 4]
>>> midpoint = len(a) // 2
>>> a[:midpoint]
[0, 1]
>>> a[midpoint:]
[2, 3, 4]

edited Feb 22, 2012 at 4:20

answered Feb 22, 2012 at 4:14

senderle

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2 Comments

wim Over a year ago

this was my first guess too, but then they wouldn't be using raw_input right.. ?

senderle Over a year ago

@wim, that's true. But fortunately // works in either case. In any case, I can't imagine a reason why the OP would be getting a TypeError from the above code, other than true division.

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