Logo Questions Linux Laravel Mysql Ubuntu Git Menu
 

How to sort a list of strings numerically?

Tags:

python

sorting

People also ask

How do you sort a list of numerically strings in Python?

Python sorted() Function The sorted() function returns a sorted list of the specified iterable object. You can specify ascending or descending order. Strings are sorted alphabetically, and numbers are sorted numerically. Note: You cannot sort a list that contains BOTH string values AND numeric values.

How do you sort a list containing strings?

In Python, there are two ways, sort() and sorted() , to sort lists ( list ) in ascending or descending order. If you want to sort strings ( str ) or tuples ( tuple ), use sorted() .

How do I sort a text file numerically?

Sort a File Numerically To sort a file containing numeric data, use the -n flag with the command. By default, sort will arrange the data in ascending order. If you want to sort in descending order, reverse the arrangement using the -r option along with the -n flag in the command.


You haven't actually converted your strings to ints. Or rather, you did, but then you didn't do anything with the results. What you want is:

list1 = ["1","10","3","22","23","4","2","200"]
list1 = [int(x) for x in list1]
list1.sort()

If for some reason you need to keep strings instead of ints (usually a bad idea, but maybe you need to preserve leading zeros or something), you can use a key function. sort takes a named parameter, key, which is a function that is called on each element before it is compared. The key function's return values are compared instead of comparing the list elements directly:

list1 = ["1","10","3","22","23","4","2","200"]
# call int(x) on each element before comparing it
list1.sort(key=int)

You could pass a function to the key parameter to the .sort method. With this, the system will sort by key(x) instead of x.

list1.sort(key=int)

BTW, to convert the list to integers permanently, use the map function

list1 = list(map(int, list1))   # you don't need to call list() in Python 2.x

or list comprehension

list1 = [int(x) for x in list1]

I approached the same problem yesterday and found a module called [natsort][1], which solves your problem. Use:

from natsort import natsorted # pip install natsort

# Example list of strings
a = ['1', '10', '2', '3', '11']

[In]  sorted(a)
[Out] ['1', '10', '11', '2', '3']

[In]  natsorted(a)
[Out] ['1', '2', '3', '10', '11']

# Your array may contain strings
[In]  natsorted(['string11', 'string3', 'string1', 'string10', 'string100'])
[Out] ['string1', 'string3', 'string10', 'string11', 'string100']

It also works for dictionaries as an equivalent of sorted. [1]: https://pypi.org/project/natsort/


In case you want to use sorted() function: sorted(list1, key=int)

It returns a new sorted list.


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, ...].