Is Includes/cpython/datetime.pxd incomplete?

[Blue]

Hello!

I am trying to use CPython's API directly, but it seems like the already defined interface is incomplete. In my case PyDateTime_TimeZone_UTC is missing, and PyDateTime_FromTimestamp takes 3 arguments when it's supposed to take 2 arguments.

I am trying to change the following code into using Cython's interface of the Cpython APII:

from libc.stdint cimport int64_t

from datetime import datetime, timezone

cdef int64_t DISCORD_EPOCH = 1420070400000

cdef class Snowflake:

    cdef readonly int64_t id

    def __cinit__(self, int64_t id, *args, **kwargs):

        self.id = id

    @property

    def created_at(self):

        """Returns a datetime object of when the snowflake was created."""

        cdef unsigned long long timestamp = (self.id >> 22) + DISCORD_EPOCH

        return datetime.fromtimestamp(timestamp / 1000, tz=timezone.utc)

But this fails

from libc.stdint cimport int64_t

from cpython.datetime cimport import_datetime, PyDateTimeAPI

import_datetime()

cdef int64_t DISCORD_EPOCH = 1420070400000

cdef class Snowflake:

    cdef readonly int64_t id

    def __cinit__(self, int64_t id, *args, **kwargs):

        self.id = id

    @property

    def created_at(self):

        """Returns a datetime object of when the snowflake was created."""

        cdef int64_t timestamp = ((self.id >> 22) + DISCORD_EPOCH) / 1000

        return PyDateTimeAPI.DateTime_FromTimestamp(timestamp, 0)

Am I looking at wrong place, or is Cython in this case wrong?

[Stefan Behnel]

Blue schrieb am 18.04.21 um 15:31:

> I am trying to use CPython's API directly, but it seems like the already
> defined interface is incomplete. In my case PyDateTime_TimeZone_UTC

> <https://docs.python.org/3/c-api/datetime.html#c.PyDateTime_TimeZone_UTC> is
> missing, and PyDateTime_FromTimestamp
> <https://docs.python.org/3/c-api/datetime.html#c.PyDateTime_FromTimestamp> takes

> 3 arguments when it's supposed to take 2 arguments

> <https://docs.python.org/3/library/datetime.html#datetime.datetime.fromtimestamp>

The .pxd file was added in 2013 and it looks like it wasn't updated with
new functions since then. PR welcome that adds the newer functions.

https://github.com/cython/cython/blob/master/Cython/Includes/cpython/datetime.pxd

PyDateTime_FromTimestamp() only takes a single argument, BTW, a tuple.

Note that you can always just define these functions yourself if you need
them in your code (and send a PR anyway :) ).


> I am trying to *change *the following code into using Cython's interface of
> the Cpython API
> <https://github.com/cython/cython/blob/master/Cython/Includes/cpython/datetime.pxd>
> I:

>
> from libc.stdint cimport int64_t
> from datetime import datetime, timezone
>
> cdef int64_t DISCORD_EPOCH = 1420070400000
>
> cdef class Snowflake:
> cdef readonly int64_t id
>
> def __cinit__(self, int64_t id, *args, **kwargs):
> self.id = id
>
> @property
> def created_at(self):
> """Returns a datetime object of when the snowflake was created."""
> cdef unsigned long long timestamp = (self.id >> 22) + DISCORD_EPOCH
> return datetime.fromtimestamp(timestamp / 1000, tz=timezone.utc)
>

> *But** this fails*

Note that "this fails" is not very descriptive. Instead of hoping for
someone to copy your code into a file and compile it to find out about the
error message, it's better to just copy it right into your email when you
see it on your screen.

> from libc.stdint cimport int64_t
>
> from cpython.datetime cimport import_datetime, PyDateTimeAPI
> import_datetime()
>
> cdef int64_t DISCORD_EPOCH = 1420070400000
>
>
> cdef class Snowflake:
> cdef readonly int64_t id
>
> def __cinit__(self, int64_t id, *args, **kwargs):
> self.id = id
>
> @property
> def created_at(self):
> """Returns a datetime object of when the snowflake was created."""
> cdef int64_t timestamp = ((self.id >> 22) + DISCORD_EPOCH) / 1000
> return PyDateTimeAPI.DateTime_FromTimestamp(timestamp, 0)
>
> Am I looking at wrong place, or is Cython in this case wrong?

Neither, really. The macro (it's actually not a function) maps the
arguments internally. You probably don't want to call through the function
pointer directly. We should provide a convenience inline wrapper function
"date[time]_from_timestamp()" for the Date[Time]_FromTimestamp() functions,
just like for the other constructor functions.

Again, PR welcome.

Stefan

[Blue]

Note that "this fails" is not very descriptive. Instead of hoping for
someone to copy your code into a file and compile it to find out about the
error message, it's better to just copy it right into your email when you
see it on your screen.

Yes I understand, normally I'd include a traceback but in this case I thought I was clear with it not existing: "...but it seems like the already defined interface is incomplete. In my case PyDateTime_TimeZone_UTC is missing, and PyDateTime_FromTimestamp takes 3 arguments when it's supposed to take 2 arguments..."

 

Neither, really. The macro (it's actually not a function) maps the
arguments internally. You probably don't want to call through the function
pointer directly. We should provide a convenience inline wrapper function
"date[time]_from_timestamp()" for the Date[Time]_FromTimestamp() functions,
just like for the other constructor functions.

Again, PR welcome.

I opened #4128.