Python: Isinstance() Undefined Global Name
Solution 1:
As pointed in some comment, circular dependencies are not well handled if imported in the form from a import A
.
In short, the problem with ... import *
is that is causes the local scope to have all its declarations overridden, in effect making the identification of from which module (in your case) a class comes from. This causes exactly what you are facing.
Changing the import
statement in the following way, together with a classified reference to a.A
, produces OK
as output.
import a
classB:
def__init__(self):
self.m_tName = "B"defdo(self, tA ):
print tA
ifnotisinstance( tA, a.A ):
print ( "invalid parameter" )
print( "OK" )
As a bit of additional information, this has already been discussed in Why is "import *" bad?. I would point in special to this answer: https://stackoverflow.com/a/2454460/1540197.
**Edit:**This article explain the import confusion.
Solution 2:
You have a circular dependancy, a.py and b.py import each other.
You could move either import statement inside the method where it is used. So b.py would become:
classA:def__init__(self):
self.m_tName = "A"deftest(self):
from b import B
tB = B()
tB.do( self )
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