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There is an old [[Python debugging|Python bug]]<ref name="bug_27400" /> which ''only'' impacts embedded Python applications, such as the Kodi Python environment. The issue is that <code>datetime.strptime</code><ref name="pydocs_datetime" /> is only initialized once per process, and not every time the embedded environment is reinitialized. This causes <code>datetime.strptime</code> to return <code>None</code> (and perhaps other strange behavior).
There is an old [[Python debugging|Python bug]]<ref name="bug_27400" /> which ''only'' impacts embedded Python applications, such as the Kodi Python environment. The issue is that <code>datetime.strptime</code><ref name="pydocs_datetime" /> is only initialized once per process, and not every time the embedded environment is reinitialized. This causes <code>datetime.strptime</code> to return <code>None</code> (and perhaps other strange behavior).


=== Resolution options ===
=== Workaround ===
One option is for you to replace every reference to <code>datetime.strptime</code> to use a [[#Patch|patch]], the code of which is shown below on this page. This involves less voodoo, but there is always the possibility that some library code uses <code>strptime</code> and that will cause the potential for incorrect results or a full Kodi crash, e.g. the [[Add-on:Youtube-dl|YouTube-dl]] add-on (<kbd>script.module.youtube.dl</kbd>) was crashing Kodi for a while.
The workaround is to monkey-patch <code>datetime.strptime</code> so that any user of the Python runtime will use it. It is more voodoo-like, but situations like this are why Python ''natively supports'' [[wikipedia:Monkey patch|monkey patching]], after all. The typically excellent Python documentation manages to be both thorough and concise simultaneously with regards to <code>datetime.strptime</code> and is well worth reviewing before deciding which angle of attack best suits your use case.<ref name="pydocs_strptime" />; it discusses some of the differences between <code>datetime.strptime</code> and <code>time.strptime</code>.<ref name="pydocs_differences" />
 
The other option is to monkey-patch <code>datetime.strptime</code> so that any user of the Python runtime will use it. It is more voodoo-like, but situations like this are why Python ''natively supports'' [[wikipedia:Monkey patch|monkey patching]], after all. The typically excellent Python documentation manages to be both thorough and concise simultaneously with regards to <code>datetime.strptime</code> and is well worth reviewing before deciding which angle of attack best suits your use case.<ref name="pydocs_strptime" />; it discusses some of the differences between <code>datetime.strptime</code> and <code>time.strptime</code>.<ref name="pydocs_differences" />


=== Patch ===
=== Patch ===
This patch simply replaces <code>datetime.strptime</code> with <code>time.strptime</code> as they are nearly identical in function. The original Kodi-specific implementation and its commit history are available on GitHub as part of <code>script.module.kutils</code>.<ref name="kutils_source" /> Essentially, the patch is:
This patch simply replaces <code>datetime.strptime</code> with <code>time.strptime</code> as they are nearly identical in function. The original Kodi-specific implementation and its commit history are available on GitHub as part of <code>script.module.kutils</code>.<ref name="kutils_source" /> Essentially, the patch is:
<syntaxhighlight lang="python">
<syntaxhighlight lang="python">
    @staticmethod
import datetime
    def monkey_patch_strptime():
import time
        # Check if problem exists (don't want to stomp on patch applied earlier)
 
        try:
 
            datetime.datetime.strptime('0', '%H')
class proxydt(datetime.datetime):
        except TypeError:
 
            # Globally replace Python's datetime.datetime.strptime with
     @classmethod
            # the version here.
     def strptime(cls, date_string, format):
            datetime.datetime = StripTimePatch.strptime
         return datetime.datetime(*(time.strptime(date_string, format)[:6]))
     @staticmethod
 
     def strptime(date_string: str, date_format: str) -> datetime.datetime:
 
         result: datetime.datetime
datetime.datetime = proxydt
        result = datetime.datetime(*(time.strptime(date_string, date_format)[0:6]))
        return result
</syntaxhighlight>
</syntaxhighlight>
== asyncio ==
It is a known [https://github.com/python/cpython/issues/91375 issue] that <code>asyncio</code> module or rather its C-based implementation does not support embedded Python environments that use sub-interpreters, such as Kodi Python environment. Essentially it means that only one addon can start the event loop by calling <code>asyncio.run()</code> and others will fail with <code>RuntimeError</code>.
=== Workaround ===
The workaround is to disable C-based <code>asyncio</code> module and use its pure-Python implementation. This can be done by the following code that should be put at the beginning of your addon entrypoint script:
<syntaxhighlight lang="python">
import sys
sys.modules['_asyncio'] = None
</syntaxhighlight>
You will loose possible performance benefits of <code>asyncio</code> but your async Python code won't fail.


== References ==
== References ==

Latest revision as of 19:44, 1 September 2022

Home icon grey.png   ▶ Development ▶ Add-on development ▶ About Add-ons ▶ Python Problems


This page is meant to document Python issues of general interest to Kodi addon developers.

datetime.strptime

There is an old Python bug[1] which only impacts embedded Python applications, such as the Kodi Python environment. The issue is that datetime.strptime[2] is only initialized once per process, and not every time the embedded environment is reinitialized. This causes datetime.strptime to return None (and perhaps other strange behavior).

Workaround

The workaround is to monkey-patch datetime.strptime so that any user of the Python runtime will use it. It is more voodoo-like, but situations like this are why Python natively supports monkey patching, after all. The typically excellent Python documentation manages to be both thorough and concise simultaneously with regards to datetime.strptime and is well worth reviewing before deciding which angle of attack best suits your use case.[3]; it discusses some of the differences between datetime.strptime and time.strptime.[4]

Patch

This patch simply replaces datetime.strptime with time.strptime as they are nearly identical in function. The original Kodi-specific implementation and its commit history are available on GitHub as part of script.module.kutils.[5] Essentially, the patch is: 

import datetime
import time


class proxydt(datetime.datetime):

    @classmethod
    def strptime(cls, date_string, format):
        return datetime.datetime(*(time.strptime(date_string, format)[:6]))


datetime.datetime = proxydt

asyncio

It is a known issue that asyncio module or rather its C-based implementation does not support embedded Python environments that use sub-interpreters, such as Kodi Python environment. Essentially it means that only one addon can start the event loop by calling asyncio.run() and others will fail with RuntimeError.

Workaround

The workaround is to disable C-based asyncio module and use its pure-Python implementation. This can be done by the following code that should be put at the beginning of your addon entrypoint script: 

import sys
sys.modules['_asyncio'] = None

You will loose possible performance benefits of asyncio but your async Python code won't fail.

References

  1. ↑ Weinberg, Denny (June 27, 2016). Issue #71587: Datetime NoneType after calling Py_Finalize and Py_Initialize. Python Issue Tracker on GitHub.
  2. ↑ Python 3 Documentation (August 28, 2022). The Python Standard Library » Data Types » datetime — Basic date and time types ― classmethod datetime.strptime(date_string, format) ― from the source code found in Lib/datetime.py.
  3. ↑ Python 3 Documentation (August 28, 2022). datetime — Basic date and time types » strftime() and strptime() Behavior.
  4. ↑ Python 3 Documentation (August 28, 2022). strftime() and strptime() Behavior » Technical Detail.
  5. ↑ lib/kutils/strptime_patch.py (January 11, 2022) in script.module.kutils, "A helper module for Kodi development" on GitHub.
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