Error in executing python code- dictionary problem

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)

but when I do this return, it gives me an error and final is the directory that I have made with lists of keys and values

The error is:

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

Answer 1

This error

KeyError: 'W'

means that the key you requested ('W') is not one of the keys that are stored in the dictionary. This is because your dictionary key is 'west' not 'W' (see your previous question). Try this instead:

key = { 'N' : 'north', 'S' : 'south', 'E' : 'east', 'W' : 'west' }[direction]
dx, dy =  Actions._directions[key]

Alternatively, make sure you pass the string 'west' to directionToVector and not the string 'W'.

Answer 2

Actions._directions is presumably a dictionary, so the line:

dx, dy =  Actions._directions[direction]

at runtime (based on the error message) is:

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

and it's complaining that there's no key "W" in that dictionary. So you should check to see that you've actually added that key with some value in there. Alternatively, you can do something like:

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

where (0, 0) can be any default value you choose when there's no such key. Another possibility is to handle the error explicitly:

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