why there is error of 'NameError: name 'position' is not defined'

Question

Why is it that when I run this code, the error is

'name position is not defined??'

I think I have already defined position before call it

the code is for using r,l,i,d to change the position(x,y)

def get_position_in_direction(position, direction):

    position=(0,1)
    x,y=position
    direction=input("Please enter an action (enter '?' for help): ")

    if direction=='r':
        xi,yi=(1,0)
    elif direcrion=='l':
        xi,yi=(-1,0)
    elif direction=='u':
        xi,yi=(0,1)
    elif direction=='d':
        xi,yi=(0,-1)
    else:
       pass
    position=position+xi,yi
    return position
print(get_position_in_direction(position, direction))

You define position inside the function (line 3) move it outside (line 1 or second to last) — Sayse, Aug 15 '19 at 09:11
Possible duplicate of [Short description of the scoping rules?](https://stackoverflow.com/questions/291978/short-description-of-the-scoping-rules) — WiseDev, Aug 15 '19 at 09:30
"i think i have already defined position before call it" Why do you think that? — MisterMiyagi, Aug 15 '19 at 10:56

ivallesp · Answer 1 · 2019-08-15T09:30:28.027

I find several problems in your code:

When you call it, in this line: print(get_position_in_direction(position, direction)), position and direction are not defined
The parameters direction and position are useless as input for the function, because you update them afterwards, so let's remove the lines where you update them
In the if-else statements there is a misspelling, you wrote direcrion instead of direction.
This line does not do what you want to do. See below the way of doing it correctly: position=position+xi,yi
If you enter a wrong direction, xi and yi will be undefined. Let's drop a controlled error in that case

The correct code would be:

def get_position_in_direction(position, direction):

    x,y=position    
    if direction=='r':
        xi,yi=(1,0)
    elif direction=='l':
        xi,yi=(-1,0)
    elif direction=='u':
        xi,yi=(0,1)
    elif direction=='d':
        xi,yi=(0,-1)
    else:
        raise ValueError("The value specified for the direction"
                         "parameter is not recognised as a valid parameter")
    position=(position[0]+xi, position[1]+yi)
    return position

position = (0,0)
direction = 'l'
print(get_position_in_direction(position, direction))

if you enter the `else` block, then `xi, yi` would be undefined. Therefore you could trigger an error still. Also, according to your logic about `direction`, `position might as well be removed as an argument`. — WiseDev, Aug 15 '19 at 09:22

why there is error of 'NameError: name 'position' is not defined'

1 Answers1