Question

I have a string of variable length and I know the index position is 25. As it’s variable in his length (>= 25), I need a way to locate the negative index of that same position for easier data manipulation.

Do you have any idea how this can be done?

Answer 1

I’m not sure if this is what you’re after, but if you have the index of a string, the ‘negative’ index is just the negative of the length of the string minus the index:

In [1]: import string

In [2]: s = string.ascii_letters

In [3]: s
Out[3]: 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ'

In [4]: s[25]
Out[4]: 'z'

In [5]: -(len(s)-25)
Out[5]: -27

In [6]: s[-(len(s)-25)]
Out[6]: 'z'

Or using the example from the comments:

In [7]: s = range(1, 7)

In [8]: s[4]
Out[8]: 5

In [9]: neg = -(len(s)-4) # Here you would replace 4 with your index

In [10]: s[neg]
Out[10]: 5