尝试添加列表元素时字典中的关键错误

Question

我正在尝试在具有此最终重组的字典中添加计数：{'stationA':[2,3], 'stationB':[1,0]}

 if start_station_name not in my_station_dict:
                my_station_dict["station_name"]=start_station_name
                my_station_dict[start_station_name][0]=0
 my_station_dict[start_station_name][0] += 1

 if stop_station_name not in my_station_dict:
            my_station_dict["station_name"] = stop_station_name
            my_station_dict[stop_station_name][1] = 0
 my_station_dict[stop_station_name][1] += 1

但是我明白了

my_station_dict[start_station_name][0]=0
KeyError: 'N 6 St & Bedford Ave'

Answer 1

my_station_dict["station_name"]=start_station_name

您正在将“station_name”添加为字典中的键，但随后尝试使用键 start_station_name 访问它。需要明确的是，您的代码正在创建这个：

{'station_name': 'N 6 St & Bedford Ave'}

当你真的想要这个时：

{'N 6 St & Bedford Ave': [0, 0]}

这是一个简单的更新：

if start_station_name not in my_station_dict:
    my_station_dict[start_station_name] = [0, 0]
my_station_dict[start_station_name][0] += 1

if stop_station_name not in my_station_dict:
    my_station_dict[stop_station_name] = [0, 0]
my_station_dict[stop_station_name][1] += 1

Answer 2

这里有一种方法可以满足您的要求：

my_station_dict = {}

def foo(start_station_name, stop_station_name):
    if start_station_name not in my_station_dict:
        my_station_dict[start_station_name]=[0]*2
    my_station_dict[start_station_name][0] += 1

    if stop_station_name not in my_station_dict:
        my_station_dict[stop_station_name]=[0]*2
    my_station_dict[stop_station_name][1] += 1

trips = [['A', 'B'], ['A', 'C'], ['A', 'D'], ['B', 'C'], ['D', 'B']]
for start, stop in trips:
    foo(start, stop)

print(my_station_dict)

输出：

{'A': [3, 0], 'B': [1, 2], 'C': [0, 2], 'D': [1, 1]}

尝试添加列表元素时字典中的关键错误

Key error in dictionary when try to add a list element

python

dictionary