Python Sort Lists
Sorting a list puts its items in order. Scores and names are common items to sort.
Sort a list in place
sort() changes the list itself.
nums = [5, 2, 9, 1]
nums.sort()
print(nums)Keep the old list with sorted()
sorted() returns a new list. The old list stays as it was.
nums = [5, 2, 9, 1]
ordered = sorted(nums)
print(ordered)
print(nums)Sort from big to small
Add reverse=True inside the round brackets.
scores = [72, 95, 88]
scores.sort(reverse=True)
print(scores)Sort text fairly
key=str.lower compares the lower-case forms. Capitals then stop jumping ahead.
names = ["cherry", "Banana", "apple"]
print(sorted(names))
print(sorted(names, key=str.lower))Flip the order with reverse()
reverse() does not sort. It just turns the list around.
letters = ["a", "b", "c"]
letters.reverse()
print(letters)Example
scores = [72, 95, 88, 60]
scores.sort(reverse=True)
print(scores)
names = ["Zoe", "adam", "Mia", "bob"]
names.sort(key=str.lower)
print(names)Key points
- Use sort() to sort a list in place
- Use sorted() to get a new sorted list and keep the old one
- Use reverse=True to sort from big to small
- Key: a rule Python uses to compare items while sorting
- Use reverse() to flip the current order without sorting
- Sorting puts the items of a list in order.
- Use key=str.lower for a fair text sort.
In this example, scores starts out of order. sort(reverse=True) puts the biggest score first. print(scores) shows the scores from high to low. names then holds four names with mixed capitals. sort(key=str.lower) compares the lower-case forms of the names. print(names) shows the names in fair alphabetical order.
Note
Text sorts by character codes, so capital letters come before small letters.
Try it Yourself
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Exercise
You need a sorted copy, and the old list must stay unchanged. Which code does that?