如何对同时包含数字和字母的列表进行排序？

Question

I am trying to join and sort some list that contains numbers and letters

for example:

l1 = ['AF', '0.167']
l2 = ['AF', '1']

l3 = ['AC', '1']
l4 = ['AC', '6']

if I join l1 and l2 together, l3 and l4 together and reverse them (wish letters come first), I will get two different results.

['0.167', 'AF', '1']
['1', 'AF', '0.167']
--------------------
['6', '1', 'AC']
['AC', '1', '6']

why the second one can sort properly , but the first one only switch the positions of numbers.

if I expect to get : new1 =['AF', '0.167, 1'] , new2 = ['AC', '1, 6'] How can I change the code.

The code is here:

l1 = ['AF', '0.167']
l2 = ['AF', '1']
l3 = ['AC', '1']
l4 = ['AC', '6']
new1 = l1 + l2
new1 = list(set(new1))
new2 = l3 + l4
new2 = list(set(new2))

list(reversed(new1))  
list(reversed(new2))

print( new1 )
print(list(reversed(new1))  )
print('--------------------')
print( new2 )
print(list(reversed(new2))  )

Answer 1

There are a couple of things that need to be clarified:

• Sets are unordered, doing list(set(thing)) will give you a list with "random" order
• reversed() does exactly what it sounds like, it enables you to iterate in reversed order, it doesn't do any sorting. If you want sorting, use sorted()

If I understand correctly, you want your strings to come first, followed by the sorted "numbers" (which are actually strings containing representation of numbers).

To do this, you'll need an appropriate sorting function. Something like the following should work:

>>> test1 = ['0.167', 'AF', '1']
>>> test2 = ['6', '1', 'AC']
>>> sort_key = lambda s: float('-inf') if s.isalpha() else float(s)
>>> sorted(test1, key=sort_key)
['AF', '0.167', '1']
>>> sorted(test2, key=sort_key)
['AC', '1', '6']

Depending on your data, having dict with strings as keys and a list of numbers as value might make more sense for storing it, and would be simpler to sort.