Python Codewars：有人可以解释 how/why 发生这种情况吗？

Question

我正在做 Codewars，但被这个简单的问题卡住了。问题是：

Your goal in this kata is to implement a difference function, which subtracts one list from another and returns the result. It should remove all values from list a, which are present in list b keeping their order. If a value is present in b, all of its occurrences must be removed from the other.

这是我试过的：

def array_diff(a, b):
    if a == []: return b
    if b == []: return a
    for occurrence in b:
      if occurrence in a:
        a.remove(occurrence)
    return a

由于某种原因我有 2 次失败的测试，这些失败测试的要求是：

a was [1,2,2], b was [2], expected [1]: [1, 2] should equal [1]

a was [], b was [1,2], expected []: [1, 2] should equal []

任何人都可以帮助我并在可能的情况下解释一下吗？任何帮助表示赞赏。编辑：我的借口是我是 Python 的初学者所以，如果这个问题太明显了，我很抱歉 errors/mistakes

Answer 1

您可以尝试修改您的代码如下：

def array_diff(a, b):
    if a == []: return a
    if b == []: return a
    for occurrence in b:
        if occurrence in a:
            a = list(filter(lambda val: val != occurrence, a)
    return a

Answer 2

我修好了。如果有人遇到同样的问题，这里是代码：第一个代码是Matthias提供的，比较干净，请使用。

def array_diff(a, b):    
    return [value for value in a if value not in b]
    # CREDITS TO MATTHIAS FOR THIS SIMPLE SOLUTION

我的代码，如果有人感兴趣的话：

def array_diff(a, b):
    #if a == []: return b
    #if b == []: return a
    # these if statements are replaced by the"for item in range" code below
    for occurrence in b:
      if occurrence in a:
        for item in range(a.count(occurrence)):
            a.remove(occurrence)
    return a

Python Codewars：有人可以解释 how/why 发生这种情况吗？

Python Codewars: can someone explain how/why this happens?

python

arrays

multiple-occurrence