Sorting a list having pairs without comma by first element in Python-CodePudding

I have a list that looks like below:

list = ['8 4', '4 3', '15 8', '10 5', '']

I want to sort this by the first element of each pair in descending order. That is, my output should look like the below.

sortedlist = ['15 8', '8 4', '10 5', '4 3' '']

How do I achieve this?

CodePudding user response：

You can use str.split and use first element of each pair.

lst  = ['8 4', '4 3', '15 8', '10 5', '']


def key_sort(x):
    try:
        return int(x.split()[0]) # '8 4'.split() -> ['8', '4']
    except IndexError:
        # for handling empty string : `''`
        return float('-inf')

lst.sort(key=key_sort, reverse = True)
print(lst)

Output:

['15 8', '10 5', '8 4', '4 3', '']

CodePudding user response：

With

lst  = ['8 4', '4 3', '15 8', '10 5', '']

Try:

sorted(lst, key=lambda x: int(x.split()[0]) if len(x) else float("-inf"), reverse = True)

outputs:

['15 8', '10 5', '8 4', '4 3', '']

CodePudding user response：

Something like this: (use the helper sort_key)

L = ['8 4', '4 3', '15 8', '10 5']


def sort_key(x):
    tp = x.split()
    return -(int(tp[0]))   #, int(tp[1])  <--- updated based on feedback

>>>sorted(L, key=sort_key)
['15 8', '10 5', '8 4', '4 3']