How to sort a list of strings numerically?

Question

I know that this sounds trivial but I did not realize that the sort() function of Python was weird. I have a list of \"numbers\" that are actually in string for

Answer 1

You can also use:

import re

def sort_human(l):
    convert = lambda text: float(text) if text.isdigit() else text
    alphanum = lambda key: [convert(c) for c in re.split('([-+]?[0-9]*\.?[0-9]*)', key)]
    l.sort(key=alphanum)
    return l

This is very similar to other stuff that you can find on the internet but also works for alphanumericals like [abc0.1, abc0.2, ...].

Answer 2

Seamus Campbell's answer doesnot work on python2.x.
list1 = sorted(list1, key=lambda e: int(e)) using lambda function works well.

Answer 3

Python's sort isn't weird. It's just that this code:

for item in list1:
   item=int(item)

isn't doing what you think it is - item is not replaced back into the list, it is simply thrown away.

Anyway, the correct solution is to use key=int as others have shown you.

Answer 4

Try this, it’ll sort the list in-place in descending order (there’s no need to specify a key in this case):

Process

listB = [24, 13, -15, -36, 8, 22, 48, 25, 46, -9]
listC = sorted(listB, reverse=True) # listB remains untouched
print listC

output:

 [48, 46, 25, 24, 22, 13, 8, -9, -15, -36]

Answer 5

If you want to use strings of the numbers better take another list as shown in my code it will work fine.

list1=["1","10","3","22","23","4","2","200"]

k=[]    
for item in list1:    
    k.append(int(item))

k.sort()
print(k)
# [1, 2, 3, 4, 10, 22, 23, 200]

Answer 6

The most recent solution is right. You are reading solutions as a string, in which case the order is 1, then 100, then 104 followed by 2 then 21, then 2001001010, 3 and so forth.

You have to CAST your input as an int instead:

sorted strings:

stringList = (1, 10, 2, 21, 3)

sorted ints:

intList = (1, 2, 3, 10, 21)

To cast, just put the stringList inside int ( blahblah ).

Again:

stringList = (1, 10, 2, 21, 3)

newList = int (stringList)

print newList

=> returns (1, 2, 3, 10, 21)