Hello,
I am CPython 3.4+ user on Linux.
I am writing a little library for myself to improve the traceback module --
print_exc() and friends. I want to include the module name, class name (if
possible), and function name.
Some background: traceback.print_exc() iterates through traceback objects
returned by sys.exc_info()[2]. traceback.tb_frame holds each stack frame. (I
call this 'frame' below.)
My improved library nearly works, but I noticed a strange corner case around
frame.f_locals['__class__'].
When super().__init__() is called, a 'magic' local appears in frame.f_locals
called '__class__'. Helpfully, it has the correct class for the context, which
will differ from type(self). (I discovered this magic local by poking around
in the debugger. I am unable to find any official documentation on it.)
Here is the quirk: In the last class in a chain of super.__init__() calls, this
magic local disappears. So I have no idea the correct class for the context.
I am stuck with frame.f_locals['self'].
How can I recover the correct class for the context in the last __init__()
method?
I noticed if I chance the last class to inherit from object, the magic local
'__class__' appears again.
A little code to demonstrate:
# do not subclass object here
def class X:
def __init__(self):
# frame.f_locals['__class__'] does not exist
pass
def class Y(X):
def __init__(self):
# frame.f_locals['__class__'] == Y
super().__init__()
def class Z(Y):
def __init__(self):
super().__init__()
# subclass object here
def class X2(object):
def __init__(self):
# frame.f_locals['__class__'] == X2
pass
def class Y2(X2):
def __init__(self):
# frame.f_locals['__class__'] == Y2
super().__init__()
def class Z2(Y2):
def __init__(self):
super().__init__()
Thanks,
Arpe
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