Importing Module To Use Variables In A Second Module

[rshepard]

I'm stymied by what should be a simple Python task: accessing the value of
a variable assigned in one module from within a second module. I wonder if
someone here can help clarify my thinking. I've re-read Chapter 16 (Module
Basics) in Lutz and Ascher's "Learning Python" but it's not working for me.

In one module (the "source"), variablePage.py, three wxPython widgets
display values that are assigned to variables: curVar, UoDlow, and UoDhigh.
I want to display then in equivalent widgets on a wxPython notebook tab in a
different module, the "importer."

At the top of the importer module I have:

from variablePage import curVar, UoDlow, UoDhigh

and I try to display the values of those variables in widgets on this page.
But, python complains:

from variablePage import curVar, UoDlow, UoDhigh
ImportError: cannot import name curVar

I've also tried

import variablePage as VP

and referenced the variables as VP.curVar, VP.UoDlow, and VP.UoDhigh, but
python still doesn't like this:

File "/data1/eikos/fuzSetPage.py", line 364, in loadParVar
first = VP.curVar
AttributeError: 'module' object has no attribute 'curVar'

Both of these forms are used in the book (pages 260-261) in simple
examples. I also get errors if I try importing using the class name before
the variable name.

A clue stick would be very helpful since I am not seeing just what I'm
doing incorrectly.

Rich

 

[Steve Holden]

I'm stymied by what should be a simple Python task: accessing the value of
a variable assigned in one module from within a second module. I wonder if
someone here can help clarify my thinking. I've re-read Chapter 16 (Module
Basics) in Lutz and Ascher's "Learning Python" but it's not working for me.

In one module (the "source"), variablePage.py, three wxPython widgets
display values that are assigned to variables: curVar, UoDlow, and UoDhigh.
I want to display then in equivalent widgets on a wxPython notebook tab in a
different module, the "importer."

At the top of the importer module I have:

from variablePage import curVar, UoDlow, UoDhigh

and I try to display the values of those variables in widgets on this page.
But, python complains:

from variablePage import curVar, UoDlow, UoDhigh
ImportError: cannot import name curVar

I've also tried

import variablePage as VP

and referenced the variables as VP.curVar, VP.UoDlow, and VP.UoDhigh, but
python still doesn't like this:

File "/data1/eikos/fuzSetPage.py", line 364, in loadParVar
first = VP.curVar
AttributeError: 'module' object has no attribute 'curVar'

Both of these forms are used in the book (pages 260-261) in simple
examples. I also get errors if I try importing using the class name before
the variable name.

A clue stick would be very helpful since I am not seeing just what I'm
doing incorrectly.

Rich

Self-evidently you are *not* creating the variables you think you are in
the variablePage module. Have you tried an interactive test? Try this at
the interpreter prompt:

and you will see exactly what names the module is defining in its
namespace. You could also try

to make sure that you are importing the module you think you are.

Otherwise, do you have circular imports? In other words, does the
variablePage module by any chance import the module that's trying to
import *it*? That's also a fruitful source of errors.

regards
Steve
--
Steve Holden +1 571 484 6266 +1 800 494 3119
Holden Web LLC/Ltd http://www.holdenweb.com
Skype: holdenweb http://del.icio.us/steve.holden

Sorry, the dog ate my .sigline

 

[rshepard]

Self-evidently you are *not* creating the variables you think you are in
the variablePage module. Have you tried an interactive test? Try this at
the interpreter prompt:


and you will see exactly what names the module is defining in its
namespace. You could also try


to make sure that you are importing the module you think you are.

Steve,

Many thanks.

I _think_ the problem is that the wxPython objects are not instatiated
when I'm trying to access the variables. Since they are instance variables,
they just don't exist yet.

Learning just when wxPython objects are instantiated is something I've
just begun to do.

Rich

 

[Steve Holden]

Steve,

Many thanks.

I _think_ the problem is that the wxPython objects are not instatiated
when I'm trying to access the variables. Since they are instance variables,
they just don't exist yet.

Learning just when wxPython objects are instantiated is something I've
just begun to do.

Rich

That could be. If they are instance variables, however, you will find
you have to access them as

variablePage.instancename.attributename

regards
Steve
--
Steve Holden +1 571 484 6266 +1 800 494 3119
Holden Web LLC/Ltd http://www.holdenweb.com
Skype: holdenweb http://del.icio.us/steve.holden

Sorry, the dog ate my .sigline

 

[Calvin Spealman]

Most problems like this are caused by trying to access the attributes
of the module before that module is fully executed, and thus before
they are defined.

For example, if you have A.py:
import B
data = "TEST"

And B.py:
import A
print A.data

Now, if you run A,py, it will import B before it defines its global
variable 'data', so that when the B module tries to import A and then
print A.data, it has not been defined yet. Look into the possibility
that such an import loop is occurring in your code. You can import in
loops, but not if you access things defined globally in one from a
global scope in another.