Prev: constructing and using large lexicon in a program
Next: let optionparse.Optionparser ignore unknown command line switches.
From: Chris Hare on 2 Aug 2010 15:33
I am having a problem getting around this variable namespace thing.

Consider these code bits

File a.py
from Tkinter import *
import a1

def doAgain():
x = a1.Net()
x.show("Again!")

root = Tk()
root.title("test")
f = Frame(root,bg="Yellow")
l = Button(root,text="window 1",command=doAgain)
f.grid()
l.grid()
a = 5
x = a1.Net()
x.show("window 2")
if __name__ == "__main__":
root.mainloop()

File a1.py
from Tkinter import *

class Net:
def __init__(self):
self.window = Toplevel()
def show(self,t):
self.l = Label(self.window,text=t)
self.l.grid()
button = Button(self.window, text="Again")
button.bind("<Button-1>", self.Again)
button2 = Button(self.window, text="Dismiss")
button2.bind("<Button-1>", self.hide)
button.grid()
button2.grid()
def Again(self,event):
x = Net()
x.show(a)
def hide(self,event):
self.window.destroy()


When I run a.py, it imports a1.py and click on the Again button, I get the error

Exception in Tkinter callback
Traceback (most recent call last):
File "/System/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/lib-tk/Tkinter.py", line 1410, in __call__
return self.func(*args)
File "/Volumes/Development/py/a1.py", line 17, in Again
x.show(a)
NameError: global name 'a' is not defined

I believe this is the expected behavior. so my question is this -- how do I tell the code in a1.py about the variable a, which exists in a.py? Do I have to pass it as part of the function call, or what? using

global a

in a1.py doesn't change anything.

since I am using SQLite for the disk database, I was thinking I could keep all the "global" variables in an in memory database and just access them when I need to, but other ideas are welcome.

Thanks,
Chris

From: Thomas Jollans on 2 Aug 2010 15:48
On 08/02/2010 09:33 PM, Chris Hare wrote:
> I am having a problem getting around this variable namespace thing.
>
> Consider these code bits
>
> File a.py
> from Tkinter import *
> import a1
>
> def doAgain():
> x = a1.Net()
> x.show("Again!")
>
> root = Tk()
> root.title("test")
> f = Frame(root,bg="Yellow")
> l = Button(root,text="window 1",command=doAgain)
> f.grid()
> l.grid()
> a = 5
> x = a1.Net()
> x.show("window 2")
> if __name__ == "__main__":
> root.mainloop()
>
> File a1.py
> from Tkinter import *
>
> class Net:
> def __init__(self):
> self.window = Toplevel()
> def show(self,t):
> self.l = Label(self.window,text=t)
> self.l.grid()
> button = Button(self.window, text="Again")
> button.bind("<Button-1>", self.Again)
> button2 = Button(self.window, text="Dismiss")
> button2.bind("<Button-1>", self.hide)
> button.grid()
> button2.grid()
> def Again(self,event):
> x = Net()
> x.show(a)
> def hide(self,event):
> self.window.destroy()
>
>
> When I run a.py, it imports a1.py and click on the Again button, I get the error
>
> Exception in Tkinter callback
> Traceback (most recent call last):
> File "/System/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/lib-tk/Tkinter.py", line 1410, in __call__
> return self.func(*args)
> File "/Volumes/Development/py/a1.py", line 17, in Again
> x.show(a)
> NameError: global name 'a' is not defined
>
> I believe this is the expected behavior. so my question is this -- how do I tell the code in a1.py about the variable a, which exists in a.py? Do I have to pass it as part of the function call, or what? using
>
> global a
>
> in a1.py doesn't change anything.
>
> since I am using SQLite for the disk database, I was thinking I could keep all the "global" variables in an in memory database and just access them when I need to, but other ideas are welcome.

"global" in Python isn't the same as "global" in C, or in PHP.

"Global" is, in essence, a shorter way of saying "within the scope of
this module" -- which keeps the "global" nice and clean.

You should probably just pass in the object you call "a" when creating
the object that uses it, or when calling the function/method when
calling it. If you don't want to do that, you can simply import the
module where your global data is stored -- beware of "from XYZ import
....", though - that copies the variables, and won't do you much good here.
From: Dave Angel on 2 Aug 2010 15:54
Chris Hare wrote:
> I am having a problem getting around this variable namespace thing.
>
> Consider these code bits
>
> File a.py
> from Tkinter import *
> import a1
>
> def doAgain():
> x =1.Net()
> x.show("Again!")
>
> root =k()
> root.title("test")
> f =rame(root,bg="Yellow")
> l =utton(root,text="window 1",command=doAgain)
> f.grid()
> l.grid()
> a =
> x =1.Net()
> x.show("window 2")
> if __name__ ="__main__":
> root.mainloop()
>
> File a1.py
> from Tkinter import *
>
> class Net:
> def __init__(self):
> self.window =oplevel()
> def show(self,t):
> self.l =abel(self.window,text=t)
> self.l.grid()
> button =utton(self.window, text="Again")
> button.bind("<Button-1>", self.Again)
> button2 =utton(self.window, text="Dismiss")
> button2.bind("<Button-1>", self.hide)
> button.grid()
> button2.grid()
> def Again(self,event):
> x =et()
> x.show(a)
> def hide(self,event):
> self.window.destroy()
>
>
> When I run a.py, it imports a1.py and click on the Again button, I get the error
>
> Exception in Tkinter callback
> Traceback (most recent call last):
> File "/System/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/lib-tk/Tkinter.py", line 1410, in __call__
> return self.func(*args)
> File "/Volumes/Development/py/a1.py", line 17, in Again
> x.show(a)
> NameError: global name 'a' is not defined
>
> I believe this is the expected behavior. so my question is this -- how do I tell the code in a1.py about the variable a, which exists in a.py? Do I have to pass it as part of the function call, or what? using
>
> global a
>
> in a1.py doesn't change anything.
>
> since I am using SQLite for the disk database, I was thinking I could keep all the "global" variables in an in memory database and just access them when I need to, but other ideas are welcome.
>
> Thanks,
> Chris
>
>
>
First rule is never have circular referencing between modules. In other
words, since a.py imports a1.py, a.py can refer to things in a1.py, but
never the other way around. Any time you need to look backwards, find
another means.

One approach is to create another module c.py as a container to hold
those things that both a and a1 need. That way they both import c, and
there's no problem.

Another approach is to pass the global from a.py into a1.py, and use it
that way.

And since you only have these two modules, you could just define it in
a1.py, and reference it from a.py as
a1.a

I would point out that using the same name for a module and a global
variable is bad practice. it certainly makes it hard to describe in
this case.

HTH,
DaveA
From: MRAB on 2 Aug 2010 16:03
Chris Hare wrote:
> I am having a problem getting around this variable namespace thing.
>
> Consider these code bits
>
> File a.py
> from Tkinter import *
> import a1
>
> def doAgain():
> x = a1.Net()
> x.show("Again!")
>
> root = Tk()
> root.title("test")
> f = Frame(root,bg="Yellow")
> l = Button(root,text="window 1",command=doAgain)
> f.grid()
> l.grid()
> a = 5
> x = a1.Net()
> x.show("window 2")
> if __name__ == "__main__":
> root.mainloop()
>
> File a1.py
> from Tkinter import *
>
> class Net:
> def __init__(self):
> self.window = Toplevel()
> def show(self,t):
> self.l = Label(self.window,text=t)
> self.l.grid()
> button = Button(self.window, text="Again")
> button.bind("<Button-1>", self.Again)
> button2 = Button(self.window, text="Dismiss")
> button2.bind("<Button-1>", self.hide)
> button.grid()
> button2.grid()
> def Again(self,event):
> x = Net()
> x.show(a)
> def hide(self,event):
> self.window.destroy()
>
>
> When I run a.py, it imports a1.py and click on the Again button, I get the error
>
> Exception in Tkinter callback
> Traceback (most recent call last):
> File "/System/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/lib-tk/Tkinter.py", line 1410, in __call__
> return self.func(*args)
> File "/Volumes/Development/py/a1.py", line 17, in Again
> x.show(a)
> NameError: global name 'a' is not defined
>
> I believe this is the expected behavior. so my question is this -- how do I tell the code in a1.py about the variable a, which exists in a.py? Do I have to pass it as part of the function call, or what? using
>
> global a
>
> in a1.py doesn't change anything.
>
> since I am using SQLite for the disk database, I was thinking I could keep all the "global" variables in an in memory database and just access them when I need to, but other ideas are welcome.
>
Why in a database? If you need the modules to share it then you could
put it in a shared module and refer to it there:

File a.py
---------
import my_globals
....
my_globals.a = 5


File a1.py
----------
import my_globals
....
x.show(my_globals.a)
From: Ethan Furman on 2 Aug 2010 16:04
Chris Hare wrote:
> I am having a problem getting around this variable namespace thing.
>
> Consider these code bits
>
> File a.py
> from Tkinter import *
> import a1
>
> def doAgain():
> x = a1.Net()
> x.show("Again!")
>
> root = Tk()
> root.title("test")
> f = Frame(root,bg="Yellow")
> l = Button(root,text="window 1",command=doAgain)
> f.grid()
> l.grid()
> a = 5
> x = a1.Net()
> x.show("window 2")
> if __name__ == "__main__":
> root.mainloop()
>
> File a1.py
> from Tkinter import *
>
> class Net:
> def __init__(self):
> self.window = Toplevel()
> def show(self,t):
> self.l = Label(self.window,text=t)
> self.l.grid()
> button = Button(self.window, text="Again")
> button.bind("<Button-1>", self.Again)
> button2 = Button(self.window, text="Dismiss")
> button2.bind("<Button-1>", self.hide)
> button.grid()
> button2.grid()
> def Again(self,event):
> x = Net()
> x.show(a)
> def hide(self,event):
> self.window.destroy()
>
>
> When I run a.py, it imports a1.py and click on the Again button, I get the error
>
> Exception in Tkinter callback
> Traceback (most recent call last):
> File "/System/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/lib-tk/Tkinter.py", line 1410, in __call__
> return self.func(*args)
> File "/Volumes/Development/py/a1.py", line 17, in Again
> x.show(a)
> NameError: global name 'a' is not defined
>
> I believe this is the expected behavior. so my question is this -- how do I tell the code in a1.py about the variable a, which exists in a.py? Do I have to pass it as part of the function call, or what? using
>
> global a
>
> in a1.py doesn't change anything.

The global keyword does not make a variable global. It tells the
interpreter that the variable in question can be find in the module
scope, not the function/method scope. In other words, the variable is
global to the module, but not to the whole program.

What you'll need to do is pass a into Net when you instanciate it, like
so (untested):

def doAgain():
x = a1.Net(a)
x.show("Again!")

and in Net:

class Net:
def __init__(self, some_number):
self.some_number = some_number
self.window = Toplevel()
.
.
.
def Again(self,event):
x = Net(self.some_number)
x.show()

Keep in mind, though, that if you change a in a.py after you've
instanciated Net, your Net instance will not see the change. For the
change to show up, a would need to be mutable, and you would have to
mutate it. The other option is to change the Net instance's some_number
directly (i.e. x.some_number = 9).

Hope this helps.

~Ethan~
 |  Next  |  Last
Pages: 1 2
Prev: constructing and using large lexicon in a program
Next: let optionparse.Optionparser ignore unknown command line switches.