Python - Sort Lists
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)
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Example
Sort the list numerically:
thislist = [100, 50, 65, 82, 23]
thislist.sort()
print(thislist)
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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)
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Example
Sort the list descending:
thislist = [100, 50, 65, 82, 23]
thislist.sort(reverse = True)
print(thislist)
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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)
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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)
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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)
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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)
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