Question

How to sort a list of lists by the first item in sub-list in ascending order with Python

Answer 1

def get_first_item(item):
    return item[0]

lst = [[4, 3], [7, 5], [3, 1], [5, 9], [1, 4], [6, 9]]

lst = sorted(lst, key=get_first_item)

print(lst)


'''
run:

[[1, 4], [3, 1], [4, 3], [5, 9], [6, 9], [7, 5]]

'''

 

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Answer 2

lst = [[4, 3], [7, 5], [3, 1], [5, 9], [1, 4], [6, 9]]

lst.sort()

print(lst)


'''
run:

[[1, 4], [3, 1], [4, 3], [5, 9], [6, 9], [7, 5]]

'''

 

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Answer 3

import operator

lst = [[4, 3, 5], [7, 5, 8], [3, 1, 6], [5, 9, 3], [1, 4, 2], [6, 9, 1]]

lst = sorted(lst, key=operator.itemgetter(0))

print(lst)


'''
run:

[[1, 4, 2], [3, 1, 6], [4, 3, 5], [5, 9, 3], [6, 9, 1], [7, 5, 8]]

'''

 

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Answer 4

lst = [[4, 3, 5], [7, 5, 8], [3, 1, 6], [5, 9, 3], [1, 4, 2], [6, 9, 1]]

lst.sort(key=lambda x: x[0])

print(lst)


'''
run:

[[1, 4, 2], [3, 1, 6], [4, 3, 5], [5, 9, 3], [6, 9, 1], [7, 5, 8]]

'''

 

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