将字符串列表转换为唯一的小写，保持顺序(Python 2.7)

Question

我想将字符串列表转换为小写并在保留顺序的同时删除重复项。我在StackOverflow上发现的许多单行Python魔力将字符串列表转换为小写，但似乎顺序丢失了。

我已经编写了下面的代码，它实际上有效，我很高兴坚持下去。但我想知道是否有一种方法可以做到这一点，它更 pythonic 和更少的代码（如果我将来要写类似的东西，可能会更少错误。这个花了我相当长的时间才写出来）。

def word_list_to_lower(words):
    """ takes a word list with a special order (e.g. frequency)
    returns a new word list all in lower case with no uniques but preserving order"""
    print("word_list_to_lower")    
    # save orders in a dict
    orders = dict()
    for i in range(len(words)):
        wl = words[i].lower()
        # save index of first occurence of the word (prioritizing top value)        
        if wl not in orders:
            orders[wl] = i
    # contains unique lower case words, but in wrong order
    words_unique = list(set(map(str.lower, words)))
    # reconstruct sparse list in correct order
    words_lower = [''] * len(words)
    for w in words_unique:
        i = orders[w]
        words_lower[i] = w
    # remove blank entries
    words_lower = [s for s in words_lower if s!='']
    return words_lower

Answer 1

稍微修改答案 如何在保持顺序的同时从列表中删除重复项？

def f7(seq):
    seen = set()
    seen_add = seen.add
    seq = (x.lower() for x in seq)
    return [x for x in seq if not (x in seen or seen_add(x))]

Answer 2

你也可以做：

pip install orderedset

然后：

from orderedset import OrderedSet
initial_list = ['ONE','one','TWO','two','THREE','three']
unique_list =  [x.lower() for x in list(OrderedSet(initial_list))]
print unique_list

Answer 3

只需执行以下操作：

initial_list = ['ONE','one','TWO','two']
uninique_list =  [x.lower() for x in list(set(initial_list))]
print unique_list

Answer 4

initial_list = ['ONE','one','TWO','two']
new_list = []
[new_list.append(s.lower()) for s in initial_list if s.lower() not in new_list]