python - python代码执行出错-字典问题

Question

while stack.isEmpty() != 1:
             fin = stack.pop()
         print fin            - output is (1,1)
         k = final.get(fin)
         return k

def directionToVector(direction, speed = 1.0):
    dx, dy =  Actions._directions[direction]
    return (dx * speed, dy * speed)
  directionToVector = staticmethod(directionToVector)

但是当我返回时，它给我一个错误，final 是我用键和值列表创建的目录

错误是:

File "line 212, in directionToVector
    dx, dy =  Actions._directions[direction]
KeyError: 'W'

Answer 1

Actions._directions 大概是一个字典，所以行:

dx, dy =  Actions._directions[direction]

在运行时(基于错误信息)是:

dx, dy =  Actions._directions["W"]

它提示说字典中没有键“W”。所以你应该检查你是否真的添加了那个带有一些值的键。或者，您可以执行以下操作:

dx, dy =  Actions._directions.get(direction, (0, 0))

其中 (0, 0) 可以是您在没有此类键时选择的任何默认值。另一种可能性是显式处理错误:

try:
    dx, dy =  Actions._directions[direction]
except KeyError:
    # handle the error for missing key