4 ms·

Why not something like this: def f_iter(many, args): while True: m = f(many, args) if m: yield m else:

Why not something like this: def f_iter(many, args): while True: m = f(many, args) if m: yield m else: raise StopIteration ... for m in f_iter(many, args): # do stuff with m This way you’re isolating all the initialization logic, error handling, etc. And you can focus on your domain logic in your client code.

repsilat 7y ago
And less reasonably, something similar for regular expressions: for m in filter([re.match(...)], bool): ... ;-)
mlevental 7y ago
so i should write a whole other function that iterates over a list instead of being happy that := exists?
- throwaway744678 7y ago
  Yes! No pain, no gain!
ciupicri 7y ago
Instead of raising StopIteration you could also just return from the function. You could also make it a bit shorter if you swap the if branches. def f_iter(many, args): while True: m = f(many, args) if not m: return yield m
- zb 7y ago
  Instead of raising StopIteration you have to return from the function, otherwise you'll just get a RuntimeError starting with Python 3.7.
  - ciupicri 7y ago
    You're right. The [changelog] for Python 3.7 states: > [bpo-32670]: Enforce [PEP 479] for all code. This means that manually raising a StopIteration exception from a generator is prohibited for all code, regardless of whether ‘from __future__ import generator_stop’ was used or not. [changelog]: https://docs.python.org/3.7/whatsnew/changelog.html#id115 https://docs.python.org/3.7/whatsnew/changelog.html#id115 [bpo-32670]: https://bugs.python.org/issue32670 https://bugs.python.org/issue32670 [PEP 479]: https://www.python.org/dev/peps/pep-0479/ https://www.python.org/dev/peps/pep-0479/
bvrmn 7y ago
Python has built-in facilities for that, there is no need to write wrapper by yourself. from functools import partial with open('mydata.db', 'rb') as f: for block in iter(partial(f.read, 64), b''): process_block(block)

repsilat 7y ago

And less reasonably, something similar for regular expressions: for m in filter([re.match(...)], bool): ... ;-)

mlevental 7y ago

so i should write a whole other function that iterates over a list instead of being happy that := exists?

throwaway744678 7y ago
Yes! No pain, no gain!

ciupicri 7y ago

Instead of raising StopIteration you could also just return from the function. You could also make it a bit shorter if you swap the if branches. def f_iter(many, args): while True: m = f(many, args) if not m: return yield m

zb 7y ago
Instead of raising StopIteration you have to return from the function, otherwise you'll just get a RuntimeError starting with Python 3.7.
- ciupicri 7y ago
  You're right. The [changelog] for Python 3.7 states: > [bpo-32670]: Enforce [PEP 479] for all code. This means that manually raising a StopIteration exception from a generator is prohibited for all code, regardless of whether ‘from __future__ import generator_stop’ was used or not. [changelog]: https://docs.python.org/3.7/whatsnew/changelog.html#id115 https://docs.python.org/3.7/whatsnew/changelog.html#id115 [bpo-32670]: https://bugs.python.org/issue32670 https://bugs.python.org/issue32670 [PEP 479]: https://www.python.org/dev/peps/pep-0479/ https://www.python.org/dev/peps/pep-0479/

bvrmn 7y ago

Python has built-in facilities for that, there is no need to write wrapper by yourself. from functools import partial with open('mydata.db', 'rb') as f: for block in iter(partial(f.read, 64), b''): process_block(block)