Reversing a string in python

Question

I want to find a palindrome in a string.

mystring = "1234321"

Why does

mystring[3:7:-1]

not work, but

second = mystring[3:7]
reversed = second[::-1]

this work?

dhg · Accepted Answer · 2012-04-13 15:35:20Z

7

Because you have to tell python to "start" with the end index and "end" with the start index:

>>> "0123456789"[7:3:-1]
'7654'

answered Apr 13, 2012 at 15:35

dhg

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1 Comment

In the case of the OP's example, mystring[6:2:-1]

JerseyMike · Accepted Answer · 2012-04-13 15:40:28Z

0

When you reversing the string on the fly like that, you need to put the larger index first. You should use:

mystring[7:3:-1]

instead of:

mystring[3:7:-1]

answered Apr 13, 2012 at 15:40

JerseyMike

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mike · Accepted Answer · 2012-04-13 15:44:06Z

0

mystring[::-1] implies the start and the end.

Using [3:7:-1] you give an "increment", start index and finish index, but you are also instantly out of your string boundaries....

answered Apr 13, 2012 at 15:44

mike

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