[Python-Dev] PEP 288: Generator Attributes (original) (raw)

Jack Jansen Jack.Jansen@cwi.nl
Fri, 22 Nov 2002 11:35:28 +0100

On Friday, Nov 22, 2002, at 09:46 Europe/Amsterdam, Raymond Hettinger wrote:

def outputCaps(logfile): while True: line = self.data logfile.write(line.upper) yield None outputCaps.data = "" # optional attribute initialization

g = outputCaps(open('logfil.txt','w')) for line in open('myfile.txt'): g.data = line g.next()

I don't like it, there's "Magic! Magic!" written all over it. Generators have always given me that feeling (you start reading them as a function, then 20 lines down you meet a "yield" and suddenly realize you have to start reading at the top again, keeping in mind that this is a persistent stack frame), but with the self plus the fact that you local variables may not be what they appear to be makes it hairy. You basically cannot understand the code without knowing the code of the caller. There's also absolutely no way to get encapsulation. So count me in for a -1.

Generators have to me always felt more "class-instance-like" than "function-like", and I guess this just goes to show it.