Weird callback execution order in Twisted?
- by SlashV
Consider the following code:
from twisted.internet.defer import Deferred
d1 = Deferred()
d2 = Deferred()
def f1(result):
print 'f1',
def f2(result):
print 'f2',
def f3(result):
print 'f3',
def fd(result):
return d2
d1.addCallback(f1)
d1.addCallback(fd)
d1.addCallback(f3)
#/BLOCK====
d2.addCallback(f2)
d1.callback(None)
#=======BLOCK/
d2.callback(None)
This outputs what I would expect:
f1 f2 f3
However when I swap the order of the statements in BLOCK to
#/BLOCK====
d1.callback(None)
d2.addCallback(f2)
#=======BLOCK/
i.e. Fire d1 before adding the callback to d2, I get:
f1 f3 f2
I don't see why the time of firing of the deferreds should influence the callback execution order.
Is this an issue with Twisted or does this make sense in some way?
