Sort list of strings by position

user_8541953 0
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I have a list of strings with the following pattern

my_list = ['/path/to/my/data/S1B_IW_GRDH_1SDV_20190610T030906_20190610T030931_016628_01F4BE_6B99_VV.tif',
     '/path/to/my/data/S1A_IW_GRDH_1SDV_20190523T030954_20190523T031019_027349_0315A8_999E_VV.tif',
     '/path/to/my/data/S1A_IW_GRDH_1SDV_20190511T030953_20190511T031018_027174_03102E_402F_VV.tif',
     '/path/to/my/data/S1A_IW_GRDH_1SDV_20190628T030956_20190628T031021_027874_032595_0B1F_VV.tif',
     '/path/to/my/data/S1A_IW_GRDH_1SDV_20190604T030955_20190604T031020_027524_031B16_BD33_VV.tif',
     '/path/to/my/data/S1B_IW_GRDH_1SDV_20190622T030907_20190622T030932_016803_01F9F1_D6E9_VV.tif',
     '/path/to/my/data/S1B_IW_GRDH_1SDV_20190505T030904_20190505T030929_016103_01E4AD_17B5_VV.tif']

I want to sort my list in chronological order using the time information that is present on each string (20190610,.....). The problem is that at the begining of each string I have the pattern S1A or S1B which makes that using a simple mylist.sort() does not work directly.

Looking in others posts I have seen that the solution would be to use the key argument with some kind of pattern.

My question is, how to start the sorting at a specific position of each string in my list. In my case I want to start sorting at position 35 right after _1SDV_

I have seen some options like 

from operator import itemgetter

my_list.sort(key = itemgetter(35))

or 

my_list.sort(key = lambda x: x[35])
list sorting python
2 Answers

Copying @schwobaseggl's solution from the comments, the following solution should work.

my_list.sort(key = lambda x: x[35:])

Example:

>>> my_list = ['91', '82', '73', '64', '55', '46', '37', '28', '19']
>>> my_list.sort()
>>> my_list
['19', '28', '37', '46', '55', '64', '73', '82', '91']
>>> my_list.sort(key = lambda x: x[1:]) # sorting after first position
>>> my_list
['91', '82', '73', '64', '55', '46', '37', '28', '19']
user_71050630

Using regex:

import regex as re

my_list = ['/path/to/my/data/S1B_IW_GRDH_1SDV_20190610T030906_20190610T030931_016628_01F4BE_6B99_VV.tif',
     '/path/to/my/data/S1A_IW_GRDH_1SDV_20190523T030954_20190523T031019_027349_0315A8_999E_VV.tif',
     '/path/to/my/data/S1A_IW_GRDH_1SDV_20190511T030953_20190511T031018_027174_03102E_402F_VV.tif',
     '/path/to/my/data/S1A_IW_GRDH_1SDV_20190628T030956_20190628T031021_027874_032595_0B1F_VV.tif',
     '/path/to/my/data/S1A_IW_GRDH_1SDV_20190604T030955_20190604T031020_027524_031B16_BD33_VV.tif',
     '/path/to/my/data/S1B_IW_GRDH_1SDV_20190622T030907_20190622T030932_016803_01F9F1_D6E9_VV.tif',
     '/path/to/my/data/S1B_IW_GRDH_1SDV_20190505T030904_20190505T030929_016103_01E4AD_17B5_VV.tif']

my_list.sort(key=lambda x: re.findall("\d{8}", x)[0])

print(my_list)

Output:

['/path/to/my/data/S1B_IW_GRDH_1SDV_20190505T030904_20190505T030929_016103_01E4AD_17B5_VV.tif',
 '/path/to/my/data/S1A_IW_GRDH_1SDV_20190511T030953_20190511T031018_027174_03102E_402F_VV.tif',
 '/path/to/my/data/S1A_IW_GRDH_1SDV_20190523T030954_20190523T031019_027349_0315A8_999E_VV.tif',
 '/path/to/my/data/S1A_IW_GRDH_1SDV_20190604T030955_20190604T031020_027524_031B16_BD33_VV.tif',
 '/path/to/my/data/S1B_IW_GRDH_1SDV_20190610T030906_20190610T030931_016628_01F4BE_6B99_VV.tif',
 '/path/to/my/data/S1B_IW_GRDH_1SDV_20190622T030907_20190622T030932_016803_01F9F1_D6E9_VV.tif',
 '/path/to/my/data/S1A_IW_GRDH_1SDV_20190628T030956_20190628T031021_027874_032595_0B1F_VV.tif']
user_80807580
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