Python – Differential Sort String Numbers and Alphabets

Given a List String, Reorder List, with Sorted Alphabets followed by Sorted Strings.

Input : test_list = [“1”, “G”, “10”, “L”, “9”, “K”, “4”] 
Output : [‘G’, ‘K’, ‘L’, ‘1’, ‘4’, ‘9’, ’10’] 
Explanation : Alphabets sorted, succeeded by sorted digits.

Input : test_list = [“1”, “G”, “10”, “L”, “9”] 
Output : [‘G’, ‘L’, ‘1’, ‘9’, ’10’] 
Explanation : Alphabets sorted, succeeded by sorted digits. 

Method #1 : Using isnumeric() + loop

In this, we separate numeric and alphabetic characters, using isnumeric(), and then perform sort on each list, then perform join of both lists for obtaining result. Works with only 1 digit numbers string.

Python3

# Python3 code to demonstrate working of
# Differential Sort String Numbers and Alphabets
# Using isnumeric() + loop

# initializing list
test_list = ["1", "G", "7", "L", "9", "M", "4"]

# printing original list
print("The original list is : " + str(test_list))

numerics = []
alphabets = []
for sub in test_list:

    # checking and inserting in respective container
    if sub.isnumeric():
        numerics.append(sub)
    else:
        alphabets.append(sub)

# attaching lists post sort
res = sorted(alphabets) + sorted(numerics)

# printing result
print("The Custom sorted result : " + str(res))

Output

The original list is : ['1', 'G', '7', 'L', '9', 'M', '4']
The Custom sorted result : ['G', 'L', 'M', '1', '4', '7', '9']

Method #2 : Using sorted() + isnumeric()

This is one liner way to solve this problem, it checks for numerics using isnumeric, and sorted() is used to perform sort(). Converts elements to integers and tests, can handle more than 1 digit numbers. 

Python3

# Python3 code to demonstrate working of
# Differential Sort String Numbers and Alphabets
# Using sorted() + isnumeric()

# initializing list
test_list = ["100", "G", "74", "L", "98", "M", "4"]

# printing original list
print("The original list is : " + str(test_list))

# using int() to type convert to integer
# using sorted() to perform sort operation
res = sorted(test_list, key = lambda ele: (ele.isnumeric(), int(ele) if ele.isnumeric() else ele))

# printing result
print("The Custom sorted result : " + str(res))

Output

The original list is : ['100', 'G', '74', 'L', '98', 'M', '4']
The Custom sorted result : ['G', 'L', 'M', '4', '74', '98', '100']

Time Complexity: O(n*log(n))

Auxiliary Space: O(n)

Method #3 : Using isalpha()+sort()+extend() methods

Python3

# Python3 code to demonstrate working of
# Differential Sort String Numbers and Alphabets
# initializing list
test_list = ["1", "G", "7", "L", "9", "M", "4"]

# printing original list
print("The original list is : " + str(test_list))

numerics = []
alphabets = []
for sub in test_list:
    # checking and inserting in respective container
    if sub.isalpha():
        alphabets.append(sub)
    else:
        numerics.append(sub)

# attaching lists post sort
alphabets.sort()
numerics.sort()
alphabets.extend(numerics)

# printing result
print("The Custom sorted result : " + str(alphabets))

Output

The original list is : ['1', 'G', '7', 'L', '9', 'M', '4']
The Custom sorted result : ['G', 'L', 'M', '1', '4', '7', '9']

Time Complexity : O(N)
Auxiliary Space : O(N)

Method 4: Using list comprehension +  isnumeric()

The idea is to separate the numbers and alphabets into two separate lists and then sorting them separately before concatenating them.

Below is the implementation:

Python3

# Python3 code to demonstrate working of
# Differential Sort String Numbers and Alphabets
# Using two separate lists

# initializing list
test_list = ["1", "G", "7", "L", "9", "M", "4"]

# printing original list
print("The original list is : " + str(test_list))

# separating numbers and alphabets
num_list = [int(x) for x in test_list if x.isnumeric()]
alpha_list = [x for x in test_list if not x.isnumeric()]

# sorting the lists
num_list.sort()
alpha_list.sort()

# concatenating the lists
res = alpha_list + [str(x) for x in num_list]

# printing result
print("The Custom sorted result : " + str(res))

Output

The original list is : ['1', 'G', '7', 'L', '9', 'M', '4']
The Custom sorted result : ['G', 'L', 'M', '1', '4', '7', '9']

Time complexity: O(n*log(n)) because the sorting of both lists takes O(n*log(n)) time. 
Auxiliary space: O(n) because we are creating two separate lists to store the numbers and alphabets, which can take up to n space.