列表‘真’去重-刪除全部重複元素

最近遇到一個問題：在遍歷列表時刪除重複內容，不夠徹底；再解決後，來分享下我的思路

實際情景

下圖是某張表的記錄【僅考慮這些字段】，直接看來，就感覺大部分都是重複的，全部去重後也就三條；但在腳本，執行我寫的方法後 ，結果還是很多條，我就有些犯迷糊了，沒頭緒。

實際我用的代碼如下：

        for i in abc:
            if abc.count(i) != 1:
                abc.remove(i)

爲了不泄露公司的數據，用列表abc來分享：

    def test_012(self):
        abc = [('115', 'C2019093015002', 1569826868000, 1569826868000),
               ('115', 'C2019093015002', 1569826868000, 1569826868000),
               ('115', 'C2019093015002', 1569826868000, 1569826868000),
               ('115', 'C2019093015002', 1569826868000, 1569826868000),
               ('115', 'C2019093015002', 1569826868000, 1569826868000),
               ('66666', 'C2019093015002', 1569826868000, 1569826868000),
               ('66666', 'C2019093015002', 1569826868000, 1569826868000),
               ('66666', 'C2019093015002', 1569826868000, 1569826868000),
               ('66666', 'C2019093015002', 1569826868000, 1569826868000),
               66666, 66666, 66666, 66666,
               7878, 7878]
        print(len(abc), '最初的長度')

        for i in abc:
            if abc.count(i) != 1:
                abc.remove(i)
        print(len(abc), '處理後的長度')

這一部分是我第一版的代碼，感覺沒毛病呢。執行結果卻是：

但肉眼看着就覺得不對；若是全部去重，肯定是4條啊，爲什麼會是7條呢。

解決方法

上面的思路是：對列表abc做個遍歷，若當前元素在列表中出現的次數不等於1，就移除當前元素；但這次移除某元素後的 列表（長度、元素）實際變了。【遍歷在新的列表操作】看下圖：

那要怎樣才能實現呢？

思路1a：拿出一個不會變、元素相同的列表 來代替列表abc，因爲列表 真正的拷貝是要使用分片的方法，故而

    def test_234(self):
        abc = [('115', 'C2019093015002', 1569826868000, 1569826868000),
               ('115', 'C2019093015002', 1569826868000, 1569826868000),
               ('115', 'C2019093015002', 1569826868000, 1569826868000),
               ('115', 'C2019093015002', 1569826868000, 1569826868000),
               ('115', 'C2019093015002', 1569826868000, 1569826868000),
               ('66666', 'C2019093015002', 1569826868000, 1569826868000),
               ('66666', 'C2019093015002', 1569826868000, 1569826868000),
               ('66666', 'C2019093015002', 1569826868000, 1569826868000),
               ('66666', 'C2019093015002', 1569826868000, 1569826868000),
               66666, 66666, 66666, 66666,
               7878, 7878]
        print(len(abc), '最初的長度')
        for i in abc[:]:
            if abc.count(i) != 1:
                abc.remove(i)
        print(len(abc), '處理後的長度')
        print(abc)

倒序的列表 來代替列表abc：

    def test_345(self):
        abc = [('115', 'C2019093015002', 1569826868000, 1569826868000),
               ('115', 'C2019093015002', 1569826868000, 1569826868000),
               ('115', 'C2019093015002', 1569826868000, 1569826868000),
               ('115', 'C2019093015002', 1569826868000, 1569826868000),
               ('115', 'C2019093015002', 1569826868000, 1569826868000),
               ('66666', 'C2019093015002', 1569826868000, 1569826868000),
               ('66666', 'C2019093015002', 1569826868000, 1569826868000),
               ('66666', 'C2019093015002', 1569826868000, 1569826868000),
               ('66666', 'C2019093015002', 1569826868000, 1569826868000),
               66666, 66666, 66666, 66666,
               7878, 7878]
        print(len(abc), '最初的長度')
        for i in abc[::-1]:
            if abc.count(i) != 1:
                abc.remove(i)
        print(len(abc), '處理後的長度')
        print(abc)

思路1a：拿出一個元素相同的元組 來代替列表abc

    def test_45678(self):
        abc = [('115', 'C2019093015002', 1569826868000, 1569826868000),
               ('115', 'C2019093015002', 1569826868000, 1569826868000),
               ('115', 'C2019093015002', 1569826868000, 1569826868000),
               ('115', 'C2019093015002', 1569826868000, 1569826868000),
               ('115', 'C2019093015002', 1569826868000, 1569826868000),
               ('66666', 'C2019093015002', 1569826868000, 1569826868000),
               ('66666', 'C2019093015002', 1569826868000, 1569826868000),
               ('66666', 'C2019093015002', 1569826868000, 1569826868000),
               ('66666', 'C2019093015002', 1569826868000, 1569826868000),
               66666, 66666, 66666, 66666,
               7878, 7878]
        print(len(abc), '最初的長度')
        for i in tuple(abc):
            if abc.count(i) != 1:
                abc.remove(i)
        print(len(abc), '處理後的長度')
        print(abc)

思路2：如果我非要堅持使用會變的列表abc作遍歷呢，我想到的是 讓其一直在做遍歷，直到某次遍歷前後 列表abc的長度不做改變，就跳出循環；

    def test_123(self):
        abc = [('115', 'C2019093015002', 1569826868000, 1569826868000),
               ('115', 'C2019093015002', 1569826868000, 1569826868000),
               ('115', 'C2019093015002', 1569826868000, 1569826868000),
               ('115', 'C2019093015002', 1569826868000, 1569826868000),
               ('115', 'C2019093015002', 1569826868000, 1569826868000),
               ('66666', 'C2019093015002', 1569826868000, 1569826868000),
               ('66666', 'C2019093015002', 1569826868000, 1569826868000),
               ('66666', 'C2019093015002', 1569826868000, 1569826868000),
               ('66666', 'C2019093015002', 1569826868000, 1569826868000),
               66666, 66666, 66666, 66666,
               7878, 7878]
        print(len(abc), '最初的長度')
        while True:
            length1 = len(abc)
            for i in abc:
                if abc.count(i) != 1:
                    abc.remove(i)
                    length2 = len(abc)
            if length1 == length2:
                break
        print(len(abc), '處理後的長度')
        print(abc)

思路3：把列表abc中count爲1的元素內容扔進新list

    def test_012(self):
        abc = [('115', 'C2019093015002', 1569826868000, 1569826868000),
               ('115', 'C2019093015002', 1569826868000, 1569826868000),
               ('115', 'C2019093015002', 1569826868000, 1569826868000),
               ('115', 'C2019093015002', 1569826868000, 1569826868000),
               ('115', 'C2019093015002', 1569826868000, 1569826868000),
               ('66666', 'C2019093015002', 1569826868000, 1569826868000),
               ('66666', 'C2019093015002', 1569826868000, 1569826868000),
               ('66666', 'C2019093015002', 1569826868000, 1569826868000),
               ('66666', 'C2019093015002', 1569826868000, 1569826868000),
               66666, 66666, 66666, 66666,
               7878, 7878]
        print(len(abc), '最初的長度')

        ABC = list()
        for i in abc[:]:
            if abc.count(i) != 1:
                abc.remove(i)
            else:
                ABC.append(i)

        print(len(ABC), '處理後的長度')
        print(ABC)

    def test_7892(self):
        abc = [('115', 'C2019093015002', 1569826868000, 1569826868000),
               ('115', 'C2019093015002', 1569826868000, 1569826868000),
               ('115', 'C2019093015002', 1569826868000, 1569826868000),
               ('115', 'C2019093015002', 1569826868000, 1569826868000),
               ('115', 'C2019093015002', 1569826868000, 1569826868000),
               ('66666', 'C2019093015002', 1569826868000, 1569826868000),
               ('66666', 'C2019093015002', 1569826868000, 1569826868000),
               ('66666', 'C2019093015002', 1569826868000, 1569826868000),
               ('66666', 'C2019093015002', 1569826868000, 1569826868000),
               66666, 66666, 66666, 66666,
               7878, 7878]
        print(len(abc), '最初的長度')
        temp = abc[:]
        abc.clear()
        for e in temp:
            if e not in abc:
                abc.append(e)

        print(len(abc), '處理後的長度')
        print(abc, '新的')

上面的執行結果：

思路4：如果不特別關注列表中元素的前後順序，使用set()函數

    def test_789(self):
        abc = [('115', 'C2019093015002', 1569826868000, 1569826868000),
               ('115', 'C2019093015002', 1569826868000, 1569826868000),
               ('115', 'C2019093015002', 1569826868000, 1569826868000),
               ('115', 'C2019093015002', 1569826868000, 1569826868000),
               ('115', 'C2019093015002', 1569826868000, 1569826868000),
               ('66666', 'C2019093015002', 1569826868000, 1569826868000),
               ('66666', 'C2019093015002', 1569826868000, 1569826868000),
               ('66666', 'C2019093015002', 1569826868000, 1569826868000),
               ('66666', 'C2019093015002', 1569826868000, 1569826868000),
               66666, 66666, 66666, 66666,
               7878, 7878]
        print(len(abc), '最初的長度')
        set_abc = set(abc)
        print(len(set_abc), '處理後的長度')
        print(list(set_abc), '新的')

這一部分執行的結果就有可能是：

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