如何在python 3.7中修復“運行時錯誤：字典在迭代過程中更改了大小”

Question

if __name__ == '__main__':

    students = {}

    for _ in range(int(input())):
        name = input()
        score = float(input())
        seq = {name: score}
        students.update(seq)
        a = min(students, key=students.get)

    for key, value in students.items():
        while a == min(students, key=students.get):
            del students[min(students, key=students.get)]

    print(students)

在上面的代碼中，我想刪除字典中的最小值元素。

我能夠從字典中刪除單個最小元素。 但是，如果字典中有多個相同的最低價值元素，我想刪除所有這些最低價值元素。

Answer 1

您可以對students.values()使用min來獲取最小值，

然后收集所有具有相同值的鍵，

然后將del用於所有這些鍵，如下所示：

if __name__ == '__main__':

    students = {}

    for _ in range(int(input())):
        name = input()
        score = float(input())
        seq = {name: score}
        students.update(seq)

    min_val = min(students.values())
    all_keys_with_min_val = [key for key, value in students.items() if value == min_val]

    for key in all_keys_with_min_val:
        del students[key]

    print(students)

Answer 2

最可靠的方法不是刪除條目，而是創建沒有它們的新dict 。 使用dict理解來過濾出所有得分最低的條目：

if __name__ == '__main__':
    students = {}
    for _ in range(int(input())):
        name = input()
        score = float(input())
        students[name] = score  # store directly without update
    min_score = min(students.values())  # calculate minimum only once

    students = {
        name: score for name, score in students.items()
        if score != min_score  # only keep students above minimum score
    }
    print(students)

如果要修改初始dict ，請創建一個單獨的條目列表以進行迭代：

...
min_score = min(students.values())  # calculate minimum only once

min_score_students = [name for name, score in students.items() if score == min_score]
for student in min_score_students:
    del students[key]
print(students)