Unbound Local Error with global variable

Question

I am trying to figure out why I get an UnboundLocalError in my pygame application, Table Wars. Here is a summary of what happens: The variables, `REDGOLD`, `REDCOMMAND`, `BLUEGOLD` and `BLUECOMMAND`, are initialised as global variables: ``` #Red Stat Section REDGOLD = 50 REDCOMMAND = 100 #Blue Stat Section BLUEGOLD = 50 BLUECOMMAND = 100 def main(): [...] global REDGOLD global REDCOMMAND global BLUEGOLD global BLUECOMMAND ``` This works when spawning units within the main loop, subtracting funds to spawn units. Right now, I am trying to set up a system so that when a unit dies, the killer refunds the victim's `COMMAND` and earns `GOLD` based on what he killed: ``` class Red_Infantry(pygame.sprite.Sprite): def __init__(self, screen): [...] self.reward = 15 self.cmdback = 5 [...] def attack(self): if self.target is None: return if self.target.health <= 0: REDGOLD += self.target.reward #These are the problem lines BLUECOMMAND += self.target.cmdback #They will cause the UnboundLocalError…

Accepted Answer

`global` make the global variable visible in the current code block. You only put the `global` statement in `main`, not in `attack`.

ADDENDUM

Here is an illustration of the need to use global more than once. Try this:

```
RED=1

def main():
    global RED
    RED += 1
    print RED
    f()

def f():
    #global RED
    RED += 1
    print RED

main()
```

You will get the error `UnboundLocalError: local variable 'RED' referenced before assignment`.

Now uncomment the global statement in f and it will work.

The `global` declaration is active in a LEXICAL, not a DYNAMIC scope.

Unbound Local Error with global variable

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