Open in App
Not now

# Python | Sort alternate numeric and alphabet list

• Last Updated : 20 Feb, 2023

Sometimes, while performing sorting in list, we have a problem in which we need to perform particular type of sorting in which we need to sort in alternate ways in which we have numerics and alphabets sorted in order. Lets discuss certain ways in which this task can be performed.

Method #1 : Using isalpha() + isnumeric() + zip_longest() The combination of above methods can be used to perform this task. In this, we separate the numeric and alphabets and then perform a sort on them separately and join using zip_longest().

## Python3

 `# Python3 code to demonstrate ` `# Sort alternate numeric and alphabet list` `# using isalpha() + isnumeric() + zip_longest()` `from` `itertools ``import` `zip_longest`   `# Initializing list` `test_list ``=` `[``'3'``, ``'B'``, ``'2'``, ``'A'``, ``'C'``, ``'1'``]`   `# printing original list` `print``("The original ``list` `is` `: " ``+` `str``(test_list))`   `# Sort alternate numeric and alphabet list` `# using isalpha() + isnumeric() + zip_longest()` `num_list ``=` `sorted``(``filter``(``str``.isnumeric, test_list), ` `                       ``key ``=` `lambda` `sub: ``int``(sub))`   `chr_list ``=` `sorted``(``filter``(``str``.isalpha, test_list))` `res ``=` `[ele ``for` `sub ``in` `zip_longest(num_list, chr_list)` `                              ``for` `ele ``in` `sub ``if` `ele]` `    `  `# printing result ` `print` `("``List` `after performing sorting : " ``+` `str``(res))`

Output :

```The original list is : ['3', 'B', '2', 'A', 'C', '1']
List after performing sorting : ['1', 'A', '2', 'B', '3', 'C']```

Method #2 : Using sorted() + key + lambda + isnumeric() The combination of above methods can be used to perform this task. In this, we perform the sorting in alternate manner using ord() and lambda function, testing using isnumeric().

## Python3

 `# Python3 code to demonstrate ` `# Sort alternate numeric and alphabet list` `# using sorted() + key + lambda + isnumeric()` `from` `itertools ``import` `zip_longest`   `# Initializing list` `test_list ``=` `[``'3'``, ``'B'``, ``'2'``, ``'A'``, ``'C'``, ``'1'``]`   `# printing original list` `print``("The original ``list` `is` `: " ``+` `str``(test_list))`   `# Sort alternate numeric and alphabet list` `# using sorted() + key + lambda + isnumeric()` `res ``=` `sorted``(test_list, key ``=` `lambda` `ele : (``int``(ele), ``0``)` `      ``if` `ele.isnumeric()` `      ``else` `((``ord``(ele) ``-` `64``) ``%` `26``, ``1``))`   `# printing result ` `print` `("``List` `after performing sorting : " ``+` `str``(res))`

Output :

```The original list is : ['3', 'B', '2', 'A', 'C', '1']
List after performing sorting : ['1', 'A', '2', 'B', '3', 'C']```

Method #3:

• Split the list into two lists: one for digits and one for characters.
• Sort the lists using the built-in sort() function.
• Interleave the sorted lists and create the final result list.

## Python3

 `# Python3 code to demonstrate` `# Sort alternate numeric and alphabet list`   `# Initializing list` `test_list ``=` `[``'3'``, ``'B'``, ``'2'``, ``'A'``, ``'C'``, ``'1'``]`   `# printing original list` `print``(``"The original list is : "` `+` `str``(test_list))`   `# Split the list into digits and characters` `digits ``=` `[x ``for` `x ``in` `test_list ``if` `x.isdigit()]` `chars ``=` `[x ``for` `x ``in` `test_list ``if` `x.isalpha()]`   `# Sort the lists` `digits.sort()` `chars.sort()`   `# Interleave the sorted lists` `res ``=` `[``None``] ``*` `len``(test_list)` `for` `i ``in` `range``(``len``(test_list)):` `    ``if` `i ``%` `2` `=``=` `0``:` `        ``res[i] ``=` `digits[i``/``/``2``]` `    ``else``:` `        ``res[i] ``=` `chars[i``/``/``2``]`   `# printing result` `print` `(``"List after performing sorting : "` `+` `str``(res))`

Output

```The original list is : ['3', 'B', '2', 'A', 'C', '1']
List after performing sorting : ['1', 'A', '2', 'B', '3', 'C']```

Time complexity: O(nlogn)

Auxiliary Space:O(n)

My Personal Notes arrow_drop_up
Related Articles