Given a list of strings. The task is to sort the list by the numeric part of the string.
Examples:
Input : test_list = [“Gfg34”, “is67”, “be3st”, “f23or”, “ge9eks”]
Output : [‘be3st’, ‘ge9eks’, ‘f23or’, ‘Gfg34’, ‘is67’]
Explanation : 3 < 9 < 23 < 34 < 67, numbers extracted from strings.Input : test_list = [“Gfg4”, “is67”, “be3st”, “f23or”, “ge9eks”]
Output : [‘be3st’, ‘Gfg4’, ‘ge9eks’, ‘f23or’, ‘is67’]
Explanation : 3 < 4 < 9 < 23 < 67, numbers extracted from strings.
Method #1 : Using sort() + re.findall()
In this, we perform the task of sorting using sort(), the explicit function is used to extract numbers using findall().
Python3
# Python3 code to demonstrate working of # Sort Strings on numerical substrings# Using sort() + findall()import re# helper function to perform sortdef num_sort(test_string): return list(map(int, re.findall(r'\d+', test_string)))[0]# initializing listtest_list = ["Gfg34", "is67", "be3st", "f23or", "ge9eks"]# printing original listprint("The original list is : " + str(test_list))# calling functiontest_list.sort(key=num_sort) # printing result print("Strings after numerical Sort : " + str(test_list)) |
The original list is : ['Gfg34', 'is67', 'be3st', 'f23or', 'ge9eks'] Strings after numerical Sort : ['be3st', 'ge9eks', 'f23or', 'Gfg34', 'is67']
Time Complexity: O(nlogn)
Auxiliary Space: O(n)
Method #2 : Using sort() + lambda + findall()
In this, we perform a similar function, but the difference being we use lambda function rather than an external function to perform the task of sorting.
Python3
# Python3 code to demonstrate working of # Sort Strings on numerical substrings# Using sort() + lambda + findall()import re# initializing listtest_list = ["Gfg34", "is67", "be3st", "f23or", "ge9eks"]# printing original listprint("The original list is : " + str(test_list))# findall() getting all integers.# conversion to integers using map()test_list.sort(key=lambda test_string : list( map(int, re.findall(r'\d+', test_string)))[0]) # printing result print("Strings after numerical Sort : " + str(test_list)) |
The original list is : ['Gfg34', 'is67', 'be3st', 'f23or', 'ge9eks'] Strings after numerical Sort : ['be3st', 'ge9eks', 'f23or', 'Gfg34', 'is67']
Time Complexity: O(nlogn)
Auxiliary Space: O(n)
Method #3 : Using extend(),sort() and index() methods
Python3
# Python3 code to demonstrate working of# Sort Strings on numerical substrings# initializing listtest_list = ["Gfg34", "is67", "be3st", "f23or", "ge9eks"]# printing original listprint("The original list is : " + str(test_list))x=[]dig="0123456789"for i in test_list: p="" for j in i: if j in dig: p+=j x.append(int(p))y=[]y.extend(x)x.sort()res=[]for i in x: res.append(test_list[y.index(i)]) # printing resultprint("Strings after numerical Sort : " + str(res)) |
The original list is : ['Gfg34', 'is67', 'be3st', 'f23or', 'ge9eks'] Strings after numerical Sort : ['be3st', 'ge9eks', 'f23or', 'Gfg34', 'is67']
Time Complexity : O(NlogN)
Auxiliary Space : O(N)
Method#4: Using list comprehension
Python3
import retest_list = ["Gfg34", "is67", "be3st", "f23or", "ge9eks"]print("The original list is : " + str(test_list))substrings = [int(x) for string in test_list for x in re.findall(r'\d+', string)]substrings.sort()res = [string for x in substrings for string in test_list if int(re.findall(r'\d+', string)[0]) == x]print("Strings after numerical Sort : " + str(res))#This code is contributed by Vinay Pinjala. |
The original list is : ['Gfg34', 'is67', 'be3st', 'f23or', 'ge9eks'] Strings after numerical Sort : ['be3st', 'ge9eks', 'f23or', 'Gfg34', 'is67']
Time Complexity : O(NlogN)
Auxiliary Space : O(N)
Method #5: Using isdigit() method
- Initialize the input list of strings test_list.
- Use the sorted() function to sort the list based on a key function. The key function is defined using a lambda function that takes each string x in the list and performs the following steps:
a. Use filter() to extract only the digits from the string.
b. Use join() to concatenate the digits into a single string.
c. Use int() to convert the resulting string of digits to an integer.
d. Return the integer as the sorting key. - Assign the sorted list to the variable sorted_list.
- Print the sorted list using the print() function.
Python3
#Initailizing the listtest_list = ["Gfg34", "is67", "be3st", "f23or", "ge9eks"]#printing original list before sortingprint("The original list is:",test_list)#sorting the list using the isdigit() methodsorted_list = sorted(test_list, key=lambda x: int(''.join(filter(str.isdigit, x))))#printing the result. MBprint("List after numeric sort is:",sorted_list) |
The original list is: ['Gfg34', 'is67', 'be3st', 'f23or', 'ge9eks'] List after numeric sort is: ['be3st', 'ge9eks', 'f23or', 'Gfg34', 'is67']
Time Complexity : O(NlogN)
Auxiliary Space : O(N)
