python3下filter過濾None時的問題和解決辦法

問題：

形如，對比a_1和b_1，找出b_1中缺失的數

a_1 = [5, 9, 6, 7, 2, 8, 1, 4, 3, 0]
b_1 = [5, 9, 6, 7, 9, 3, 4, 5, 9, 3]
b_miss = [None if b_1.__contains__(j) else j for i, j in enumerate(a_1)]
b_filter = filter(None, b_miss)
b_miss_filter = list(b_filter)

 

# 希望預期結果
b_miss_filter = [2, 8, 1, 0]
# 實際結果卻爲
b_miss_filter = [2, 8, 1]

原因：

filter(None, a)函數進行數據過濾空值None,默認會把0、false這樣具體的值過濾掉。

解決：

a_1 = [5, 9, 6, 7, 2, 8, 1, 4, 3, 0]
b_1 = [5, 9, 6, 7, 9, 3, 4, 5, 9, 3]
b_miss = [None if b_1.__contains__(j) else j for i, j in enumerate(a_1)]
b_filter = filter(lambda x: x is not None, b_miss)  # 將None換爲過濾規則函數
b_miss_filter = list(b_filter)

用函數方式去定義過濾規則，其中，lambda形式比較簡潔。