如何从 python 中的字符串中提取部分值？

Question

I have the following string:

(1, 2, 3, 4)

I want to convert it to just the last two values:

(3, 4)

In my actual code all four fields are whole numbers but vary greatly in length. I've tried doing this with both regex and 'for' statements as well as trying the various answers to similar questions here on SO but so far no luck.

Answer 1

This gives you the last two terms in your tuple:

>> a = (1,2,3,4)
>> a[-2:]
(3,4)

Answer 2

It sounds like you want to use the slice operator .

Edit: Perhaps this is a better link. Scroll down a bit for the slice notation stuff. The examples deal with strings, but it should work with any sequence type.

Answer 3

If (1,2,3,4) is tuple:

data = (1,2,3,4)
newData = data[-2:]

If you have '(1,2,3,4)' then:

import ast
data = ast.literal_eval('(1,2,3,5)')
newData = data[-2:]

Or in case you have to split such list in a certain value:

def get_slice(inputData, searchVal):   
    if searchVal in inputData and inputData.index(searchVal) < len(inputData):
        return inputData[inputData.index(searchVal)+1:]
    return ()

get_slice((1,2,3,4),2)