Question

I know it’s a heavily discussed topic, I know there are tons of threads out there about it (I’ve read them all), but I still Just Don’t Get It.

Undefined variables (both local and global) are my biggest problem in Python and I have no idea what I’m doing when trying to fix them. I’ll go through and add an x = 0 or a var = func(var) some where and some times it works and sometimes it doesn’t. It’s incredibly frustrating and I really need some help. I’ve asked my teacher but it usually takes her a while to get back to me and I’d like to get this thing fixed.

Here’s what I’m working on: http://pastebin.com/KTuh7D2p (This is for school.)

Can someone please explain variable thing to me?

I keep getting errors like this:

Traceback (most recent call last):
  File "Project1-v2.py", line 144, in <module>
    main()
  File "Project1-v2.py", line 12, in main
    itemsSave = tagYell(items, itemsSale, itemsSave)
UnboundLocalError: local variable 'itemsSave' referenced before assignment

Answer 1

In this particular case, I would guess that it is because you are trying to use itemSave to define itself. This is equivalent to saying something like:

x = 5 + x

the very first time you define x.

You need to give some context as to what itemSave is before you can try and use its value.

For example, this program:

myNum = 5
x = float(myNum+x)
print x

Would give me an error message of:

x = float(myNum+x)
NameError: name 'x' is not defined

This however, would work fine, and print “15”:

myNum = 5
x = 10
x = float(myNum+x)
print x