A previous stackoverflow question explains how to sort a list of strings alpha-numerically. I would like to sort a list of tuples alphanumerically by the tuple's first element.
Example 1:
>>> sort_naturally_tuple([('b', 0), ('0', 1), ('a', 2)])
[('0', 1), ('a', 2), ('b', 0)]
Example 2:
>>> sort_naturally_tuple([('b10', 0), ('0', 1), ('b9', 2)])
[('0', 1), ('b9', 2), ('b10', 0)]
Update: To emphasize the alphanumeric factor, please review example 2.
Using the second answer from the other question, generalized to support any method on item as the basis for getting the key:
import re
from operator import itemgetter
def sorted_nicely(l, key):
""" Sort the given iterable in the way that humans expect."""
convert = lambda text: int(text) if text.isdigit() else text
alphanum_key = lambda item: [ convert(c) for c in re.split('([0-9]+)', key(item)) ]
return sorted(l, key = alphanum_key)
print sorted_nicely([('b10', 0), ('0', 1), ('b9', 2)], itemgetter(0))
This is exactly the same as that answer except generalized to use any callable as the operation on item. If you just wanted to do it on a string, you'd use lambda item: item
, if you wanted to do it on a list, tuple, dict, or set, you'd use operator.itemgetter(key_or_index_you_want)
, or if you wanted to do it on a class instance you could use operator.attrgetter('attribute_name_you_want')
.
It gives
[('0', 1), ('b9', 2), ('b10', 0)]
for your example #2.
Tuples are by default sorted by their elements, starting at the first. So simply do
L = [('b', 0), ('0', 1), ('a', 2)]
L.sort()
print L
# or create a new, sorted list
print sorted([('b', 0), ('0', 1), ('a', 2)])
The question you liked to talks about natural sorting, which is different from normal (alphanumeric) sorting.
Lets say you want to do natural sort on the first item only:
import re
def naturalize(item):
# turn 'b10' into ('b',10) which sorts correctly
m = re.match(r'(\w+?)(\d+)', item)
return m.groups()
# now sort by using this function on the first element of the tuple:
print sorted(L, key=lambda tup: naturalize(tup[0]))
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