lambda python function in reversing list

Question

scores = []
with open("scores.txt") as f:
    for line in f:
        name, score = line.split(',')
        score = int(score)
        scores.append((name, score))
        scores.sort(key=lambda s: s[1])
for name, score in scores:
    print(name + ", " + str(score))

This code can be used to show a txt file looking like this (disordered):

alpha, 3
beta, 1
gamma, 2

To looking like this:

beta, 1
gamma, 2
alpha, 3

How can I modify the code so that it instead prints as:

alpha, 3
gamma, 2
beta, 1

Duplicate? http://stackoverflow.com/questions/3940128/how-can-i-reverse-a-list-in-python — Chris_Rands, Sep 15 '16 at 12:30

score 2 · Accepted Answer · answered Sep 15 '16 at 12:28

2

Use the reverse argument to list.sort():

scores.sort(key=lambda s: s[1], reverse=True)

From the documentation:

reverse is a boolean value. If set to True, then the list elements are sorted as if each comparison were reversed.

answered Sep 15 '16 at 12:28

Eugene Yarmash

142,882
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score 2 · Answer 2 · answered Sep 15 '16 at 12:29

2

Just use scores[::-1] instead of scores in the last for-loop. Here's a small illustration of this behaviour:

a=list(range(10))
print(a[::-1])

answered Sep 15 '16 at 12:29

jadsq

3,033
3
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score 0 · Answer 3 · answered Sep 15 '16 at 12:40

Use reverse when you sort:

>>> l  = [('a', 1), ('c',5), ('a', 2), ('b', 1)]
>>> l.sort(key=lambda i: i[1], reverse=True)
>>> l
[('c', 5), ('a', 2), ('a', 1), ('b', 1)]

You can use it with sorted:

>>> l  = [('a', 1), ('c',5), ('a', 2), ('b', 1)]
>>> sorted(l, key=lambda i: i[1], reverse=True)
[('c', 5), ('a', 2), ('a', 1), ('b', 1)]
>>>

lambda python function in reversing list

3 Answers3