Python 3.11: “Zero cost” exception handling
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Python 3.11: “Zero cost” exception handling
1–10 of 96 posts
Re: Python 3.11: “Zero cost” exception handling
#2They weren't zero cost before? In a language where idiomatic control flow uses exceptions? That's crazy!
I've felt weird using exceptions like that but I always assumed that CPython was optimized to minimize overhead of exceptions and exception handlers.
Re: Python 3.11: “Zero cost” exception handling
#3They weren't zero cost before? In a language where idiomatic control flow uses exceptions? That's crazy! I've felt weird using exceptions like that but I always assumed that CPython was optimized to minimize overhead of exceptions and exception handlers.
> I've felt weird using exceptions like that
How should they be used instead? Maybe I don't understand what you mean by "idiomatic control flow uses exceptions" - could you give an example. Maybe there is some use of exceptions that I'm not quite familiar with in Python.
Re: Python 3.11: “Zero cost” exception handling
#4They weren't zero cost before? In a language where idiomatic control flow uses exceptions? That's crazy! I've felt weird using exceptions like that but I always assumed that CPython was optimized to minimize overhead of exceptions and exception handlers.
> I've felt weird using exceptions like that How should they be used instead? Maybe I don't understand what you mean by "idiomatic control flow uses exceptions" - could you give an example. Maybe there is some use of exceptions that I'm not quite familiar with in Python.
The first that came to mind is how `get()` is handled in Django's ORM. The idiomatic way to look for a single object is to use `get`, then catch a `DoesNotExist` exception:
From https://docs.djangoproject.com/en/3.2/ref/models/querysets/#...
from django.core.exceptions import ObjectDoesNotExist
try:
blog = Blog.objects.get(id=1)
entry = Entry.objects.get(blog=blog, entry_number=1)
except ObjectDoesNotExist:
print("Either the blog or entry doesn't exist.")Re: Python 3.11: “Zero cost” exception handling
#5They weren't zero cost before? In a language where idiomatic control flow uses exceptions? That's crazy! I've felt weird using exceptions like that but I always assumed that CPython was optimized to minimize overhead of exceptions and exception handlers.
> I've felt weird using exceptions like that How should they be used instead? Maybe I don't understand what you mean by "idiomatic control flow uses exceptions" - could you give an example. Maybe there is some use of exceptions that I'm not quite familiar with in Python.
Re: Python 3.11: “Zero cost” exception handling
#6They weren't zero cost before? In a language where idiomatic control flow uses exceptions? That's crazy! I've felt weird using exceptions like that but I always assumed that CPython was optimized to minimize overhead of exceptions and exception handlers.
> I've felt weird using exceptions like that How should they be used instead? Maybe I don't understand what you mean by "idiomatic control flow uses exceptions" - could you give an example. Maybe there is some use of exceptions that I'm not quite familiar with in Python.
In python, it's normal to use exceptions in place of type checking, e.g. in polymorphic functions.
Re: Python 3.11: “Zero cost” exception handling
#7They weren't zero cost before? In a language where idiomatic control flow uses exceptions? That's crazy! I've felt weird using exceptions like that but I always assumed that CPython was optimized to minimize overhead of exceptions and exception handlers.
> I've felt weird using exceptions like that How should they be used instead? Maybe I don't understand what you mean by "idiomatic control flow uses exceptions" - could you give an example. Maybe there is some use of exceptions that I'm not quite familiar with in Python.
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Re: Python 3.11: “Zero cost” exception handling
#8They weren't zero cost before? In a language where idiomatic control flow uses exceptions? That's crazy! I've felt weird using exceptions like that but I always assumed that CPython was optimized to minimize overhead of exceptions and exception handlers.
> I've felt weird using exceptions like that How should they be used instead? Maybe I don't understand what you mean by "idiomatic control flow uses exceptions" - could you give an example. Maybe there is some use of exceptions that I'm not quite familiar with in Python.
When using a for-loop over an iterator, the iterator protocol in Python says to keep returning elements until you run out, at which point you throw an exception. So every loop over an iterator or iterable object in python throws an exception when it is done. https://docs.python.org/3/library/stdtypes.html#iterator.__n...
Re: Python 3.11: “Zero cost” exception handling
#9They weren't zero cost before? In a language where idiomatic control flow uses exceptions? That's crazy! I've felt weird using exceptions like that but I always assumed that CPython was optimized to minimize overhead of exceptions and exception handlers.
> In a language where idiomatic control flow uses exceptions? That's crazy!
Seems like the opposite: if exceptions are extremely rare then you want to optimise the case where they’re not raised, at the cost of the other one.
If exceptions are common then it matters a lot less, you may even want to avoid 0ce depending on the impact on the raised case.
Re: Python 3.11: “Zero cost” exception handling
#10They weren't zero cost before? In a language where idiomatic control flow uses exceptions? That's crazy! I've felt weird using exceptions like that but I always assumed that CPython was optimized to minimize overhead of exceptions and exception handlers.
> I've felt weird using exceptions like that How should they be used instead? Maybe I don't understand what you mean by "idiomatic control flow uses exceptions" - could you give an example. Maybe there is some use of exceptions that I'm not quite familiar with in Python.
Nearly all loops are terminated by raising an exception.
https://docs.python.org/3/library/exceptions.html#StopIterat...