如果有多个元素，请从列表中删除该元素的子集

Question

If I have a list like:

[u'test_1', u'test_2', u'test_3', u'bananas_4', u'cake_5', u'bananas_6']

What would be the best way to just get the following without knowing anything else in advance?

[u'test_1', u'bananas_4', u'cake_5']

So how I see it, would be something like loop over the list, store the test and bananas somehow, and if on another iteration, see another of the same start of the string, remove that from the list.

Does anyone know the best way of achieving this?

Answer 1

My main idea uses the dictionary functionality that items are not overridden by default.

I used OrderedDict to keep the order of insertion of items.

lst = [u'test_1', u'test_2', u'test_3', u'bananas_4', u'cake_5', u'bananas_6']
d = OrderedDict()
for item in lst:
    key, val = item.split('_')
    d.setdefault(key, val) # will not override if item was there before

new_list = [key + '_' + val for key,val in d.items()]
print new_list

Output is

[u'test_1', u'bananas_4', u'cake_5']

Answer 2

Simply keep a set of your prefixes and only add items to your filtered list if they're not in the prefix list:

start = [u'test_1', u'test_2', u'test_3', u'bananas_4', u'cake_5', u'bananas_6']

seen = set()
end = []

for item in start:
    prefix = item.partition('_')[0]
    if prefix not in seen:
        end.append(item)
        seen.add(prefix)

print(end)  # ['test_1', 'bananas_4', 'cake_5']

Answer 3

I would split it into two sections. The first is to split the string in the list by "_" then you would have the raw information [test,test,test,banana,cake,banana] and another with the numbers [1,2,3,4,5,6]

You could then find the uniques of the string list with the following solution: Get unique values from a list in python . Finally append the numbers back on.