Sort List Alphanumerically
List objects have a sort() method that will sort the list alphanumerically, ascending, by default:
Example
Sort the list alphabetically:
thislist = [“orange”, “mango”, “kiwi”, “pineapple”, “banana”]
thislist.sort()
print(thislist)
Output:
[‘banana’, ‘kiwi’, ‘mango’, ‘orange’, ‘pineapple’]
Example
Sort the list numerically:
thislist = [100, 50, 65, 82, 23]
thislist.sort()
print(thislist)
Output:
[23, 50, 65, 82, 100]
Sort Descending
To sort descending, use the keyword argument reverse = True:
Example
Sort the list descending:
thislist = [“orange”, “mango”, “kiwi”, “pineapple”, “banana”]
thislist.sort(reverse = True)
print(thislist)
Output:
[‘pineapple’, ‘orange’, ‘mango’, ‘kiwi’, ‘banana’]
Example
Sort the list descending:
thislist = [100, 50, 65, 82, 23]
thislist.sort(reverse = True)
print(thislist)
Output:
[100, 82, 65, 50, 23]
Customize Sort Function
You can also customize your own function by using the keyword argument key = function.
The function will return a number that will be used to sort the list (the lowest number first):
Example
Sort the list based on how close the number is to 50:
def myfunc(n):
return abs(n – 50)
thislist = [100, 50, 65, 82, 23]
thislist.sort(key = myfunc)
print(thislist)
Output:
[50, 65, 23, 82, 100]
Case Insensitive Sort
By default the sort() method is case sensitive, resulting in all capital letters being sorted before lower case letters:
Example
Case sensitive sorting can give an unexpected result:
thislist = [“banana”, “Orange”, “Kiwi”, “cherry”]
thislist.sort()
print(thislist)
Output:
[‘Kiwi’, ‘Orange’, ‘banana’, ‘cherry’]
Luckily we can use built-in functions as key functions when sorting a list.
So if you want a case-insensitive sort function, use str.lower as a key function:
Example
Perform a case-insensitive sort of the list:
thislist = [“banana”, “Orange”, “Kiwi”, “cherry”]
thislist.sort(key = str.lower)
print(thislist)
Output:
[‘banana’, ‘cherry’, ‘Kiwi’, ‘Orange’]
Reverse Order
What if you want to reverse the order of a list, regardless of the alphabet?
The reverse() method reverses the current sorting order of the elements.
Example
Reverse the order of the list items:
thislist = [“banana”, “Orange”, “Kiwi”, “cherry”]
thislist.reverse()
print(thislist)
Output:
[‘cherry’, ‘Kiwi’, ‘Orange’, ‘banana’]