UnboundLocalError - Please help

[michaelw209]

How do I fix this? It's just an assignment for school bit it's driving me crazy. low, med, and high are supposed to be initialized at there starting values only once before the loop begins, but it won't work, here's the data.

def main():
    choice = 0
    high = 3000.0
    med = 5000.0
    low = 9000.0
    priority = 0
    size = 0.0
    frequency = 0

    
    while choice != 3:
        print '1-add a back up'
        print '2-remove a backup'
        print '3-exit program'
        choice = input  ('make a selection')
        if choice == 1:
            priority = getPriority(priority)
            if priority == 1:
                addHigh()
            elif priority == 2:
                addMed()
            elif priority == 3:
                addLow()
            else:
                print 'invalid entry'
        
                
        elif choice == 2:
            priority = getPriority(priority)
            if priority == 1:
                removeHigh()
            elif priority == 2:
                removeMed()
            elif priority == 3:
                removeLow()
            else:
                print 'invalid entry'

        elif choice == 3:
            print 'goodbye'
        else:
            print'invalid entry'


def getPriority(priority):
    print '1-high priority'
    print '2-medium priority'
    print '3-low priority'
    priority = input ('enter priority')
    return priority

def getSize():
    size = input  ('enter size in megabytes')
    return size

def getFrequency():
    frequency = input  ('enter frequency')
    return frequency


    
def addHigh():
    size = getSize()
    frequency = getFrequency()
    
    high=high - size * frequency
    if high > 0:
        print 'you have' , high , 'MB left'
    else:
        print 'insufficient space'
        high = high + size * frequency

And here's the traceback:

Traceback (most recent call last):
File "F:\programming \Lab Practicum.py", line 131, in <module>
main()
File "F:\programming \Lab Practicum.py", line 22, in main
addHigh()
File "F:\programming \Lab Practicum.py", line 69, in addHigh
high=high - size * frequency
UnboundLocalErr or: local variable 'high' referenced before assignment
>>>
PLEASE HELP!!!

[bvdet]

Please use code tags when posting code. See Posting Guidelines here.

It's a matter of scope. You assign a value of 3000.0 to identifier high inside the scope of function main(). Then you attempt to access high inside the function addHigh(). When resolving names, the interpreter first searches the local namespace. If not found, it searches the enclosing scopes from the innermost scope to the outermost. In your case, the next enclosing scope is the global scope. The global namespace for a function is always the module in which the function was defined. If not found in the global namespace, it makes one final check in the built-in namespace. If this fails, a NameError is raised. UnboundLocalErr or is a subclass of NameError and occurs if a variable is referenced before it's defined in a function.

The interpreter never looks in the namespace of function main() for high, therefore the error.

You could pass the variable as an argument to function addHigh.

def main():
    #global high
    choice = 0
    high = 3000.0
    med = 5000.0
    low = 9000.0
    priority = 0
    size = 0.0
    frequency = 0
 
 
    while choice != 3:
        print '1-add a back up'
        print '2-remove a backup'
        print '3-exit program'
        choice = input  ('make a selection')
        if choice == 1:
            priority = getPriority(priority)
            if priority == 1:
                high = addHigh(high)
                # snip


def addHigh(high)
    size = getSize()
    frequency = getFrequency()
 
    high=high - size * frequency
    if high > 0:
        print 'you have' , high , 'MB left'
    else:
        print 'insufficient space'
        high = high + size * frequency
    return high

You also could define high in the global scope and declare high as a global variable.

high = 3000.0
med = 5000.0
low = 9000.0

def main():
    choice = 0
    priority = 0
    size = 0.0
    frequency = 0
    # snip


def addHigh():
    global high
    size = getSize()
    frequency = getFrequency()
 
    high=high - size * frequency
    if high > 0:
        print 'you have' , high , 'MB left'
    else:
        print 'insufficient space'
        high = high + size * frequency

[michaelw209]

Thank you for your help. I'll try those, hope it works.