词典列表在 Python 中引发了关键错误

Question

我有一个字典列表，我想分别计算“增加”和“减少”键的值。我的脚本返回了一个关键错误，这可能是因为并非所有词典都有“增加”和“减少”两者。但我不知道如何解决它。作为 Python 初学者，我们将不胜感激。

list_of_dicts = [{"decreasing": 1}, {"increasing": 4}, {"decreasing": 1}, {"increasing": 3},{"decreasing": 1},
             {"increasing": 1}]

values1 = [a_dict["decreasing"] for a_dict in list_of_dicts]
values2 = [a_dict["increasing"] for a_dict in list_of_dicts]

print(values1)
print(values2)

预期结果是：

[1,1,1]
[4,3,1]

Answer 1

您可以使用 sum() + dict.get 和默认值 0:

values1 = sum(d.get("increasing", 0) for d in list_of_dicts)
values2 = sum(d.get("decreasing", 0) for d in list_of_dicts)

print("Increasing:", values1)
print("Decreasing:", values2)

打印：

Increasing: 29
Decreasing: 9

编辑：获取值：


values1, values2 = [], []
for d in list_of_dicts:
    if "increasing" in d:
        values1.append(d["increasing"])
    elif "decreasing" in d:
        values2.append(d["decreasing"])

print("Increasing:", values1)
print("Decreasing:", values2)

打印：

Increasing: [4, 3, 1, 5, 11, 1, 4]
Decreasing: [1, 1, 1, 1, 2, 1, 2]

Answer 2

在列表理解中添加一个if，这样可以保留好的

values1 = [a_dict["decreasing"] for a_dict in list_of_dicts if "decreasing" in a_dict]
values2 = [a_dict["increasing"] for a_dict in list_of_dicts if "increasing" in a_dict]

print(values1)  # [1, 1, 1, 1, 2, 1, 2]
print(values2)  # [4, 3, 1, 5, 11, 1, 4]

Answer 3

在处理有问题的列表理解时，将它们分解。

首先可以分解为：

values1 = list()
for a_dict in list_of_dicts:
    if a_dict.get('decreasing'):
        values1.append(a_dict.get('decreasing'))

values2 = list()
for a_dict in list_of_dicts:
    if a_dict.get('increasing'):
        values2.append(a_dict.get('increasing'))

然后再将它们带回领悟中。

list_of_dicts = [{"decreasing": 1}, {"increasing": 4}, {"decreasing": 1}, {"increasing": 3},{"decreasing": 1},
             {"increasing": 1},{"decreasing": 1}, {"increasing": 5}, {"decreasing": 2}, {"increasing": 11},
             {"decreasing": 1}, {"increasing": 1},{"decreasing": 2}, {"increasing": 4}]

values1 = [a_dict.get('decreasing') for a_dict in list_of_dicts if a_dict.get('decreasing')]
values2 = [a_dict.get('increasing') for a_dict in list_of_dicts if a_dict.get('increasing')]

values11 = list()
for a_dict in list_of_dicts:
    if a_dict.get('decreasing'):
        values11.append(a_dict.get('decreasing'))

values22 = list()
for a_dict in list_of_dicts:
    if a_dict.get('increasing'):
        values22.append(a_dict.get('increasing'))

print(values1)
print(values2)

print(values1 == values11)
print(values2 == values22)

结果

$ python testing.py
[1, 1, 1, 1, 2, 1, 2]
[4, 3, 1, 5, 11, 1, 4]
True
True

词典列表在 Python 中引发了关键错误

Dictionary list raised a key error in Python

python

dictionary

list

keyerror

结果