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Python – Sort String by Custom Integer Substrings
  • Last Updated : 01 Aug, 2020

Given a list of strings, sort strings by occurrence of substring from list.

Input : test_list = [“Good at 4”, “Wake at 7”, “Work till 6”, “Sleep at 11”], subord_list = [“11”, “7”, “4”, “6”]
Output : [‘Sleep at 11’, ‘Wake at 7’, ‘Good at 4’, ‘Work till 6’]
Explanation : Strings sorted by substring presence.

Input : test_list = [“Good at 9”, “Wake at 7”, “Work till 6”, “Sleep at 11”], subord_list = [“11”, “7”, “9”, “6”]
Output : [‘Sleep at 11’, ‘Wake at 7’, ‘Good at 9’, ‘Work till 6’]
Explanation : Strings sorted by substring presence.

Method #1 : Using sorted() + zip() + lambda + regex()

The combination of above functions can be used to solve this problem. In this, we perform task of sorting by substring using regex() and sorted(), zip() is used to produce end result.



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# Python3 code to demonstrate working of 
# Sort String by Custom Substrings
# Using sorted() + zip() + lambda + regex()
import re
  
# initializing list
test_list = ["Good at 4", "Wake at 7", "Work till 6", "Sleep at 11"]
  
# printing original list
print("The original list : " + str(test_list))
  
# initializing subtring list 
subord_list = ["6", "7", "4", "11"]
  
  
# crearing inverse mapping with index
temp_dict = {val: key for key, val in enumerate(subord_list)}
  
# custom sorting 
temp_list = sorted([[ele, temp_dict[re.search("(\d+)$", ele).group()]] \
                for ele in test_list], key = lambda x: x[1])
# compiling result
res = [ele for ele in list(zip(*temp_list))[0]]
          
# printing result 
print("The sorted list : " + str(res))

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Output

The original list : ['Good at 4', 'Wake at 7', 'Work till 6', 'Sleep at 11']
The sorted list : ['Work till 6', 'Wake at 7', 'Good at 4', 'Sleep at 11']

Method #2 : Using sorted() + zip() + comparator + regex()

This is yet another way in which this task can be performed. In this similar functionality is used as above method, difference is that comparator function is fed to sorted() rather than lambda to sort.

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# Python3 code to demonstrate working of 
# Sort String by Custom Substrings
# Using sorted() + comparator + regex()
import re
  
# helper function to solve problem
def hlper_fnc(ele):
    temp = re.search("(\d+)$", ele).group()
    return temp_dict[temp] if temp in temp_dict else int(temp)
  
# initializing list
test_list = ["Good at 4", "Wake at 7", "Work till 6", "Sleep at 11"]
  
# printing original list
print("The original list : " + str(test_list))
  
# initializing subtring list 
subord_list = ["6", "7", "4", "11"]
  
# crearing inverse mapping with index
temp_dict = {val: key for key, val in enumerate(test_list)}
  
# sorting using comparator
test_list.sort(key = lambda ele: hlper_fnc(ele))
          
# printing result 
print("The sorted list : " + str(test_list))

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Output

The original list : ['Good at 4', 'Wake at 7', 'Work till 6', 'Sleep at 11']
The sorted list : ['Good at 4', 'Work till 6', 'Wake at 7', 'Sleep at 11']

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