sorting strings by numerical value in the string in python

Question

For a list with these strings, I am trying to sort them by the numbers preceding the "_" character.

my_lst = ['25_mg', '2_mg', '200_mg', '10_mg', '5_mg']

Tried several sorts like this one: print(test.sort(key = lambda x: x.split('_')[0]))

But, the list doesn't sort as expected which would be like this:

my_lst = ['2_mg', '5_mg', '10_mg', '25_mg', '200_mg']

lambda x: int(x.split('_')[0]) typecast to int. Otherwise it's a string and it's compared character by character lexicographicallly. — Amit Vikram Singh
– Amit Vikram Singh, Commented Apr 24, 2021 at 1:36

Reti43 · Accepted Answer · 2021-04-24 01:36:26Z

1

Your sort will order the strings "25", "2", etc, so everything that starts with a "1" will come first. It seems you want to sort by their actual numerical value, so change it to

my_lst.sort(key = lambda x: int(x.split('_')[0]))
print(my_lst)

which gives

['2_mg', '5_mg', '10_mg', '25_mg', '200_mg']

answered Apr 24, 2021 at 1:36

Reti43

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