I'm hitting the recursion limit in my code (well, somewhere inside Twisted, that is), and I'd appreciate any insight as to why. I wouldn't think what I'm doing -- returning a callback from method A which calls method B, which then in turn calls method A again -- would be controversial, since I'd assume Python would be letting go of the stack for method A, but I guess there's more to it than that.
Code demonstrating the issue follows. Running it results in: File "/usr/lib/python2.5/site-packages/twisted/python/reflect.py", line 550, in accumulateBases accumulateBases(base, l, baseClass) exceptions.RuntimeError: maximum recursion depth exceeded
(This doesn't actually perfectly reflect my problem in the real code I'm working with. I'm seeing "'maximum recursion depth exceeded' in <bound method DebugInfo.__del__ of <twisted.internet.defer.DebugInfo instance at 0xb1d99b6c>>", but I assume this is coming from the same basic problem in my code.)
from twisted.internet import defer, reactor
def yo_print(s, d): print s d.callback(s) return s
def some_deferred(item): d = defer.Deferred() reactor.callLater(0, lambda: yo_print(item, d)) return d
def start(items): dl =  for item in items: dl.append(some_deferred(item)) if len(dl) > 4: break items = items[len(dl):] if dl: return defer.DeferredList(dl).addCallback(next_batch, items) reactor.stop()
def next_batch(_, items): return start(items)
if __name__ == '__main__': items =  for i in range(1651): # 1650 doesn't do it items.append(i) print start(items) reactor.run() ===================================
So I guess the rule is to never, within a callback chain, call a function which was invoked earlier in the callback chain?