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python - 为什么我不能添加strptimes，只能减去？

问题描述

这工作正常：

{{ strptime(states('input_datetime.music_alarm'), "%H:%M:%S") - strptime("10", "%M") }}

但这会引发错误：

{{ strptime(states('input_datetime.music_alarm'), "%H:%M:%S") + strptime("10", "%M") }}

states('input_datetime.music_alarm') 等于一个时间，比如 08:00:00

我正在使用 jinja2 作为 homeassistant。这是错误。

Error doing job: Task exception was never retrieved
Traceback (most recent call last):
  File "/usr/lib/python3.5/asyncio/tasks.py", line 239, in _step
    result = coro.send(None)
  File "/srv/homeassistant/lib/python3.5/site-packages/homeassistant/components/automation/__init__.py", line 336, in async_trigger
    yield from self._async_action(self.entity_id, variables)
  File "/srv/homeassistant/lib/python3.5/site-packages/homeassistant/components/automation/__init__.py", line 425, in action
    yield from script_obj.async_run(variables)
  File "/srv/homeassistant/lib/python3.5/site-packages/homeassistant/helpers/script.py", line 158, in async_run
    await self._async_call_service(action, variables)
  File "/srv/homeassistant/lib/python3.5/site-packages/homeassistant/helpers/script.py", line 187, in _async_call_service
    self.hass, action, True, variables, validate_config=False)
  File "/srv/homeassistant/lib/python3.5/site-packages/homeassistant/helpers/service.py", line 72, in async_call_from_config
    config[CONF_SERVICE_DATA_TEMPLATE], variables))
  File "/srv/homeassistant/lib/python3.5/site-packages/homeassistant/helpers/template.py", line 56, in render_complex
    for key, item in value.items()}
  File "/srv/homeassistant/lib/python3.5/site-packages/homeassistant/helpers/template.py", line 56, in <dictcomp>
    for key, item in value.items()}
  File "/srv/homeassistant/lib/python3.5/site-packages/homeassistant/helpers/template.py", line 57, in render_complex
    return value.async_render(variables)
  File "/srv/homeassistant/lib/python3.5/site-packages/homeassistant/helpers/template.py", line 132, in async_render
    return self._compiled.render(kwargs).strip()
  File "/srv/homeassistant/lib/python3.5/site-packages/jinja2/environment.py", line 1008, in render
    return self.environment.handle_exception(exc_info, True)
  File "/srv/homeassistant/lib/python3.5/site-packages/jinja2/environment.py", line 780, in handle_exception
    reraise(exc_type, exc_value, tb)
  File "/srv/homeassistant/lib/python3.5/site-packages/jinja2/_compat.py", line 37, in reraise
    raise value.with_traceback(tb)
  File "<template>", line 1, in top-level template code
TypeError: bad operand type for unary -: 'datetime.datetime'

标签： pythonjinja2

解决方案

您必须使用 timedelta 并且您的代码中有多个问题。

1/ 错误使用 datetime.datetime.strptime()

>>> import datetime
>>> print(datetime.datetime.strptime("10", "%M"))
1900-01-01 00:10:00
>>> print(datetime.datetime.strptime('08:00:00', "%H:%M:%S"))
1900-01-01 08:00:00

您必须解析完整的日期时间才能获得正确的行为。

2/ 你不能将两个日期时间相加

基本上+是禁止避免错误的，你只需要-因为你只需要在你的表达式中反转变量来获得你的负时间增量。

>>> print(type(datetime.datetime.strptime("10", "%M") - datetime.datetime.strptime('08:00:00', "%H:%M:%S")))
<class 'datetime.timedelta'>
>>> print(datetime.datetime.strptime("10", "%M") - datetime.datetime.strptime('08:00:00', "%H:%M:%S"))
-1 day, 16:10:00
>>> print(datetime.datetime.strptime('08:00:00', "%H:%M:%S") - datetime.datetime.strptime("10", "%M"))
7:50:00

您可以以相反的顺序看到这会给您错误的信息-1 day, 16:10:00，因为这无法在没有错误的情况下处理。

3/ 您可以将 timedelta 注册到您的模板

默认情况下，strptime() 在 Jinja2 中不可用，因此请使用 timedelta()...

类似的东西：

import datetime
from jinja2 import Template

jinga = Template('{{ strptime(states("input_datetime.music_alarm"), "%H:%M:%S") - timedelta(minutes=10) }} ')
jinga.globals['timedelta'] = datetime.timedelta
print(jinga.render())

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