本文列些處幾種去除在Python 列表中（list）可能存在的重復(fù)項，這在很多應(yīng)用程序中都會遇到的需求，作為程序員最好了解其中的幾種方法 以備在用到時能夠?qū)懗鲇行У某绦颉?/p>方法1：樸素方法

這種方式是在遍歷整個list的基礎(chǔ)上，將第一個出現(xiàn)的元素添加在新的列表中。

示例代碼：

# Python 3 code to demonstrate # removing duplicated from list # using naive methods # initializing listtest_list = [1, 3, 5, 6, 3, 5, 6, 1]print ('The original list is : ' + str(test_list)) # using naive method# to remove duplicated # from list res = []for i in test_list: if i not in res:res.append(i) # printing list after removal print ('The list after removing duplicates : ' + str(res))

→ 輸出結(jié)果：The original list is : [1, 3, 5, 6, 3, 5, 6, 1]The list after removing duplicates : [1, 3, 5, 6]

方法2：列表解析式

這種方式實際上是第一種方法的簡化版，它利用列表解析式，使用一行代碼就可以替代上面的循環(huán)方式。

示例代碼：

# Python 3 code to demonstrate # removing duplicated from list # using list comprehension # initializing listtest_list = [1, 3, 5, 6, 3, 5, 6, 1]print ('The original list is : ' + str(test_list)) # using list comprehension# to remove duplicated # from list res = [][res.append(x) for x in test_list if x not in res] # printing list after removal print ('The list after removing duplicates : ' + str(res))

→ 輸出結(jié)果：The original list is : [1, 3, 5, 6, 3, 5, 6, 1]The list after removing duplicates : [1, 3, 5, 6]

方法3：使用set()

這種方式是最流行的方法來去除列表中的重復(fù)元素。但該方法的最大的一個缺點就是使用過后列表中元素的順序不再繼續(xù)保持與原來一致了。

示例代碼：

# Python 3 code to demonstrate # removing duplicated from list # using set() # initializing listtest_list = [1, 5, 3, 6, 3, 5, 6, 1]print ('The original list is : ' + str(test_list)) # using set()# to remove duplicated # from list test_list = list(set(test_list)) # printing list after removal # distorted orderingprint ('The list after removing duplicates : ' + str(test_list))

→ 輸出結(jié)果：The original list is : [1, 5, 3, 6, 3, 5, 6, 1]The list after removing duplicates : [1, 3, 5, 6]

方法4：利用列表解析式 + enumerate()

該方法是在列表解析式的基礎(chǔ)上利用枚舉來去除重復(fù)元素。通過檢查元素是否已經(jīng)在列表中存在從而將其略過。這種方法可以保持列表中的元素順序不會改變。

示例代碼：

# Python 3 code to demonstrate # removing duplicated from list # using list comprehension + enumerate() # initializing listtest_list = [1, 5, 3, 6, 3, 5, 6, 1]print ('The original list is : ' + str(test_list)) # using list comprehension + enumerate()# to remove duplicated # from list res = [i for n, i in enumerate(test_list) if i not in test_list[:n]] # printing list after removal print ('The list after removing duplicates : ' + str(res))

→ 輸出結(jié)果：The original list is : [1, 5, 3, 6, 3, 5, 6, 1]The list after removing duplicates : [1, 5, 3, 6]

方法5：利用collections.OrderedDict.fromkeys()

這是完成特殊任務(wù)中最快的方法。它先是將列表中的重復(fù)項移除并返回一個字典，最后轉(zhuǎn)換成列表。這種方法對于字符串也可以進行處理。

示例代碼：

# Python 3 code to demonstrate # removing duplicated from list # using collections.OrderedDict.fromkeys()from collections import OrderedDict # initializing listtest_list = [1, 5, 3, 6, 3, 5, 6, 1]print ('The original list is : ' + str(test_list)) # using collections.OrderedDict.fromkeys()# to remove duplicated # from list res = list(OrderedDict.fromkeys(test_list)) # printing list after removal print ('The list after removing duplicates : ' + str(res))

→ 輸出結(jié)果：The original list is : [1, 5, 3, 6, 3, 5, 6, 1]The list after removing duplicates : [1, 5, 3, 6]

方法6：處理嵌套列表中的重復(fù)元素

對于多維列表（列表嵌套）中的重復(fù)元素去除。這里假設(shè)列表中元素（也是列表）它們具有相同的元素（但不一定順序相同）都被當做重復(fù)元素。那么下面使用 set() + sorted() 方法來完成任務(wù)。

示例代碼：

# Python3 code to demonstrate# removing duplicate sublist # using set() + sorted() # initializing listtest_list = [[1, 0, -1], [-1, 0, 1], [-1, 0, 1], [1, 2, 3], [3, 4, 1]] # printing original listprint('The original list : ' + str(test_list)) # using set() + sorted()# removing duplicate sublistres = list(set(tuple(sorted(sub)) for sub in test_list)) # print resultprint('The list after duplicate removal : ' + str(res))

→ 輸出結(jié)果：The original list : [[1, 0, -1], [-1, 0, 1], [-1, 0, 1], [1, 2, 3], [3, 4, 1]]The list after duplicate removal : [(-1, 0, 1), (1, 3, 4), (1, 2, 3)]

也可以利用 set() + map() + sorted()

示例代碼：

# Python3 code to demonstrate# removing duplicate sublist # using set() + map() + sorted() # initializing listtest_list = [[1, 0, -1], [-1, 0, 1], [-1, 0, 1], [1, 2, 3], [3, 4, 1]] # printing original listprint('The original list : ' + str(test_list)) # using set() + map() + sorted()# removing duplicate sublistres = list(set(map(lambda i: tuple(sorted(i)), test_list))) # print resultprint('The list after duplicate removal : ' + str(res))

→ 輸出結(jié)果：The original list : [[1, 0, -1], [-1, 0, 1], [-1, 0, 1], [1, 2, 3], [3, 4, 1]]The list after duplicate removal : [(-1, 0, 1), (1, 3, 4), (1, 2, 3)]

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