Says I haven't declared, even though I clearly have

Question

The Error is called: UnboundLocalError: local variable 'P' referenced before assignment. I want it so I can change the Pen Width with K and L, but it won't let me. Can you help me?

from gturtle import*
keyK = 75
keyL = 76
P = 10

def colorKeys(key):
if key == keyK:
    P = P - 2
elif key == keyL:
    P = P + 2

makeTurtle(keyPressed = colorKeys)
hideTurtle()

while True:
    setPenWidth(P)

score 2 · Accepted Answer · edited Jan 15 '21 at 21:07

2

If you really want to use global variable in function, you can do this:

def colorKeys(key):
  global P
  if key == keyK:
      P = P - 2
  elif key == keyL:
      P = P + 2

But generally it is a bad idea.

edited Jan 15 '21 at 21:07

quamrana

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answered Jan 15 '21 at 21:01

Arseniy

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Thanks, helped me! – Jan 15 '21 at 21:12
Glad to hear that) You can mark my answer as an answer, if you will – Arseniy Jan 15 '21 at 21:13
@arseniy, any idea what gturtle is? Im trying to help him in another post and cant seem to figure out what gturtle is. HMMMMMMMMMMMMMMMMMM – Kromydas Jan 16 '21 at 22:30
@kidwhowantstolearnpython I think this is it) tobiaskohn.ch/jython/turtle.html – Arseniy Jan 16 '21 at 22:48
I figured it out but the documentation only has 1 sample codes out of many that works. WTH – Kromydas Jan 18 '21 at 04:21

score 1 · Answer 2 · answered Jan 15 '21 at 21:00

1

Variables that are created outside a function can be referenced to in the function without error, but can not be modified. You would have to make P global, define it in colorKeys, or pass it to colorKeys like you do key.

answered Jan 15 '21 at 21:00

goalie1998

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Reid Moffat · Answer 3 · 2021-05-14T18:12:06.763

1

Your function colorKeys(key) does not have a local variable P in it. Global variables cannot be changed within functions without the 'global' keyword (using the 'global' keyword is not recommended)

To fix this, you can return the value that you want to add to P:

def colorKeys(key):
    if key == keyK:
        return -2
    elif key == keyL:
        return 2
    return 0

P += colorKeys(key)

edited May 14 '21 at 18:12

answered Jan 15 '21 at 21:06

Reid Moffat

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"Global variables cannot be changed within functions" yes they can, if you use the global statement, but they probably shouldn't, and this is a better solution – juanpa.arrivillaga Jan 15 '21 at 21:20

Says I haven't declared, even though I clearly have

3 Answers3