creating generators from function
__peter__ at web.de
Wed Dec 8 11:54:42 CET 2004
Simon Wittber wrote:
> I use a coroutine/generator framework for simulating concurrent processes.
> To do this, I write all my functions using the general form:
> while True:
> do stuff
> yield None
> To make these generator functions compatible with a standard thread
> interface, I attempted to write a decorator which converts a standard
> function into a generator function (code attached below).
> Unfortunately, I received an exception, before I could test if my idea
> would work:
> TypeError: cannot create 'generator' instances
> I guess I can go the other way, and convert a generator into a
> function, but that just doesn't seem right.
> Is there anyway solve the problem described?
Generators are just functions with an extra flag set. I tried the following
modification of your code:
from opcode import opmap
def _f(): pass
function = type(_f)
co = f.func_code
nc = [ord(x) for x in co.co_code]
for i, op in enumerate(nc[:-1]):
if op == RETURN_VALUE:
nc[i] = YIELD_VALUE
newcode = ''.join([chr(x) for x in nc])
codeobj = type(co)(co.co_argcount, co.co_nlocals, co.co_stacksize,
co.co_flags + 32, newcode, co.co_consts,
co.co_varnames, co.co_filename, co.co_name,
co.co_firstlineno, co.co_lnotab, co.co_freevars,
return function(codeobj, f.func_globals, f.func_name,
print list(itertools.islice(f(), 5))
The hardest part was to find the enumerate() bug. I agree with Steven that
converting between functions and generators by replacing return with yield
and vice versa is hardly ever useful, though.
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