how to access attributes initialized in class constructor of different py file?

Question

I have two py files. a.py and b.py inside a package called test (has __init__.py)

and I want to access attribute self.items defined in the a.py below

import b

class Window(object):
    def __init__(self):
        self.items={'Magenta':'mag','Grey':'gre','Red':'red'}
    def getMats():
        newobj=b.BAR()
        selected = newobj.type_of_mats[1]

from a different py file b.py[below] so in b.py I imported the a module i.e.

import a

#now 

obj = a.Window()
print obj.items['Magenta']
class BAR(object):
    def myMat(self):
        type_of_mats=['ground', 'corridor', 'Outdoor']

should'nt the above prints mag since or how else I should do it ?

@DanielRoseman : I get error saying maximum recursion depth exceded in cmp in ntpath.py, I am on python 2.6, I also need to access attributes from b.py to be read by a.py , so in a.py I have import b — Ciasto piekarz, Dec 10 '12 at 09:46
Then you have some other code you're not showing us. Please post some code that actually shows the problem, along with the full traceback. — Daniel Roseman, Dec 10 '12 at 09:47
@san: I was looking at the python question list; it was updated when you pressed save, saw the common error and made the edit. — Martijn Pieters, Dec 10 '12 at 09:49
@Martijin: but that was so quick, when i was going to fix u already did it ahead of me — Ciasto piekarz, Dec 10 '12 at 09:57
@san it obviously *is* important, as your update has now revealed the problem, which was not evident before. — Daniel Roseman, Dec 10 '12 at 09:58
i do not get error if I do not initialize the object? i.e. newobj=b.Bar().. how can I use getAttr to get the attribute ? — Ciasto piekarz, Dec 10 '12 at 10:32

score 1 · Accepted Answer · edited May 23 '17 at 12:21

1

see these stackoverflow questions on circular imports (a) and (b). I think it depends on the compiler / interpreter being used. In my case your code does not give me recursion depth exceeded, but this does

Hope it helps.

edited May 23 '17 at 12:21

Community

1
1

answered Dec 10 '12 at 10:05

pranshus

187
6

score 0 · Answer 2 · answered Dec 10 '12 at 10:00

Circular import. a.py imports b and b.py imports a again. Chicken/egg problem! And python cannot solve that for you, so it warns you about a maximum recursion depth (it keeps on jumping from a to b to a to b to a...).

You'll have to fix it so that the import is one-way only.

score 0 · Answer 3 · answered Dec 10 '12 at 10:00

0

You have a circular dependency: a is importing b, which is in turn importing a. Since those two imports are at module level, they can never complete.

In your case, you could fix it by moving the import b into the getMats method.

answered Dec 10 '12 at 10:00

Daniel Roseman

588,541
66
880
895

how to access attributes initialized in class constructor of different py file?

3 Answers3