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Why is this variable not defined if it is a global variable?

I create a list and try to append it to another list, but even though it is a global list it still is not defined.
I had the same issue trying to apppend a string to another list, and that had the same error so I tried to make the string a list.
sees if the player hits
def hit_or_stand():
global hit **<-- notice hit is a global variable**
if hitStand == ("hit"):
player_hand()
card = deck()
hit = []
hit.append(card)
now I need to append hit to pHand (player's hand)
def player_hand():
global pHand
deck()
pHand = []
pHand.append(card)
deck()
pHand.append(card)
pHand.append(hit) **<--- "NameError: name 'hit' is not defined"**
pHand = (" and ").join(pHand)
return (pHand)
hit_or_stand()
player_hand()

global hit
This does not declare a variable which is global. It does not create a variable which does not exist. It simply says "if you see this name in this scope, assume it's global". To "declare" a global variable, you need to give it a value.
# At the top-level
hit = "Whatever"
# Or in a function
global hit
hit = "Whatever"
The only time you need a global declaration is if you want to assign to a global variable inside a function, as the name could be interpreted as local otherwise. For more on globals, see this question.

There is a misunderstanding of the global operation in OP's post. The global inside a function tells python to use that global variable name within that scope. It doesn't make a variable into a global variable by itself.
# this is already a global variable because it's on the top level
g = ''
# in this function, the global variable g is used
def example1():
global g
g = 'this is a global variable'
# in this function, a local variable g is used within the function scope
def example2():
g = 'this is a local variable'
# confirm the logic
example1()
print( g ) # prints "this is a global variable"
example2()
print( g ) # still prints "this is a global variable"

How do I pass a variable between functions python

Here are my two functions:
def selectBadge(a):
curItem = SelectBadgeView.focus()
inter_var = SelectBadgeView.item(curItem)
ListValues = inter_var['values']
print(ListValues)
SelectedBadge.set("Selected Badge: "+str(ListValues[0]))
SelectedBadgeStr=str(ListValues[0])
return SelectedBadgeStr
def selectScout(a,SelectedBadgeStr):
print(a)
if SelectedPatrol.get()==("Selected Patrol: Please Select A Patrol"):
tk.messagebox.showerror("ERROR","Please select a Patrol")
return
if SelectedBadge.get()==("Selected Badge: Please Select A Badge"):
tk.messagebox.showerror("ERROR", "Please select a Badge")
return
print(SelectedBadgeStr)
return
I want to pass the variable SelectedBadgeStr from selectBadge() to selectScout().
The variable a is a internal variable used by the tkinter treeview widget.
a = <ButtonRelease event state=Button1 num=1 x=144 y=39>
I have tried:
return SelectedBadgeStr
However this did not work.
The function is called by:
SelectScoutView.bind('<ButtonRelease-1>', selectScout)

Did you declare SelectedBadgeStr as for example an empty string before defining the function selectBadge(a)?
So just declare it like:
SelectedBadgeStr = ''
def selectBadge(a):
curItem = SelectBadgeView.focus()
.
.
.
It should work.

You can also use a shared global variable:
Declare the variable outside of the functions use:
SelectedBadgeStr = None
At the beginning of the functions use:
global SelectedBadgeStr
Whenever you use the variable now within the functions, you access the global variable

Python Global Variables - Not Defined?

I'm running into an issue where a global variable isn't "remembered" after it's modified in 2 different functions. The variable df is supposed to be a data frame, and it doesn't point to anything until the user loads in the right file. This is similar to something I have (using pandas and tkinter):
global df
class World:
def __init__(self, master):
df = None
....
def load(self):
....
df = pd.read_csv(filepath)
def save(self):
....
df = df.append(...)
save() is always called after load(). Thing is, when I call save(), I get the error that "df is not defined." I thought df got its initial assignment in init(), and then got "updated" in load()? What am I doing wrong here?

You have to use global df inside the function that needs to modify the global variable. Otherwise (if writing to it), you are creating a local scoped variable of the same name inside the function and your changes won't be reflected in the global one.
p = "bla"
def func():
print("print from func:", p) # works, readonly access, prints global one
def func1():
try:
print("print from func:", p) # error, python does not know you mean the global one
p = 22 # because function overrides global with local name
except UnboundLocalError as unb:
print(unb)
def func2():
global p
p = "blubb" # modifies the global p
print(p)
func()
func1()
print(p)
func2()
print(p)
Output:
bla # global
print from func: bla # readonly global
local variable 'p' referenced before assignment # same named local var confusion
bla # global
blubb # changed global

for anyone coming here using python3 - try using nonlocal instead of global - a new construct introduced in python3 which allows you to mutate and read global variables in local scope

You have to use the global keyword inside the function rather than outside. All the df that you have defined inside your function are locally scoped. Here is the right way -
df = pd.DataFrame() # No need to use global here
def __init__(self, master):
global df # declare here
df = None
....
def load(self):
global df # declare here
....
df = pd.read_csv(filepath)
def save(self):
global df # declare here
....
df = df.append(...)

Return statement not working python 3

The idea of this code is, the user presses the first button and enters what they want, then they press the second button and it prints it out. Can someone please tell me why my return statement is not working? It says that 'variable' is not defined. Thanks in advance for taking the time to read my question.
from tkinter import*
def fun():
variable = input('Enter Here:')
return variable
def fun_2():
print(variable)
window = Tk()
button = Button(text = 'Button', command = fun )
button2 = Button(text = 'Button2', command = fun_2 )
button.pack()
button2.pack()
window.mainloop()

In python when you create a variable inside of a function, it is only defined within that function. Therefore other functions will not be able to see it.
In this case, you will probably want some shared state within an object. Something like:
class MyClass:
def fun(self):
self.variable = input('Enter Here:')
def fun_2(self):
print(self.variable)
mc = MyClass()
window = Tk()
button = Button(text = 'Button', command = mc.fun )
button2 = Button(text = 'Button2', command = mc.fun_2 )
button.pack()
button2.pack()

fun() may return a value, but Tkinter buttons don't do anything with that return value.
Note that I used the phrase return a value, not return a variable. The return statement passes back the value of an expression, not the variable variable here. As such, the variable variable is not made into a global that other functions then can access.
Here, you can make variable a global, and tell fun to set that global:
variable = 'No value set just yet'
def fun():
global variable
variable = input('Enter Here:')
Since you did use any assignment in fun2, variable there is already looked up as a global, and it'll now successfully print the value of variable since it now can find that name.

The problem is in in fun2(). It does not get variable as an input parameter.
def fun_2(variable):
print(variable)
But note that you have to call fun_2 now with the appropriate argument. Also, as the function stands right now, there is little point in having the function if you just do a print inside of it.
Take away message: variable is not global in Python, and as such you must pass it to each function that wants to use it.

I need a delegate class?

I have a problem that sounds like a delegation problem. I have a code like the following:
class foo(object):
def __init__(self,onEvent1="", onEvent2=""):
self.OnEvent1=onEvent1
self.OnEvent1=onEvent2
def aLoop(self):
...
#in case of event1
self.OnEvent1()
...
#in case of event2
self.OnEvent2()
EventType=0
def MyBar1():
print("Event Type1")
EventType=1
def MyBar2():
print("Event Type2")
EventType=2
myFoo=foo(MyBar1,MyBar2)
while True:
myFoo.aLoop()
if (EventType==1):
print ("EventType is 1")
EventType=0
elif (EventType==2):
print ("EventType is 2")
EventType=0
I can see the message of the print() inside the callback functions but not the print() of the messages in the while loop.
The variable EventType doesn't change its value.
What I can do?

The EventType variables in MyBar1 and MyBar2 are local variables. Any variable you bind to is a local, unless explicitly configured otherwise; assignments, function parameters, a function or class definition and names you import are all ways to bind a name.
You need to use a global statement to change this:
def MyBar1():
global EventType
print("Event Type1")
EventType=1
def MyBar2():
global EventType
print("Event Type2")
EventType=2
Note that there is little point in giving your event arguments an empty string as default argument:
def __init__(self,onEvent1="", onEvent2=""):
If they are optional, set them to None and test for that:
def __init__(self, onEvent1=None, onEvent2=None):
self.OnEvent1 = onEvent1
self.OnEvent2 = onEvent2
def aLoop(self):
...
#in case of event1
if self.OnEvent1 is not None:
self.OnEvent1()
...
#in case of event2
if self.OnEvent2 is not None:
self.OnEvent2()

EventType=0
def MyBar1():
global EventType
print("Event Type1")
EventType=1
def MyBar2():
global EventType
print("Event Type2")
EventType=2
The problem is, you need to modify a global variable, but you're creating a local one instead. You can still access the global variable without using global variable. You need this to modify it.