- Oct 1, 2006
- Reaction score
The code below exhibits different behavior depending on whether it invokes sys.settrace ('-t' option) or not. This means that (in a more complicated case) debugging the code (which uses sys.settrace) makes it fail. Any ideas?
""" Demonstrace that tracing messes up curried class definitions """ # Some simple command line parsing: -t or --trace means trace, nothing means don't trace import sys def usage( ): print 'Usage:', sys.argv[ 0 ], '[-t | --trace]' sys.exit( 1 ) if 1 == len( sys.argv ): pass elif 2 == len( sys.argv ): if sys.argv[ 1 ]=='-t' or sys.argv[ 1 ]=='--trace': def trace ( frame, event, arg ): # print frame, event, arg return trace sys.settrace( trace ) else: usage( ) else: usage( ) # The test: define a class factory with a curried member function def the_factory( parm1 ): class the_class( object ): def curried( self ): return parm1 return the_class x = the_factory( 42 ) y = x( ) try: x.parm1 print "Failure: x (the manufactured class) has attribute parm1?!" except AttributeError: print "Success with the manufactured class!" try: y.parm1 print "Failure: y (the instance) has attribute parm1?!" except AttributeError: print "Success with the instance!" assert y.curried( ) == 42, "Currying didn't work?!"