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parameter.
When you supply an ``http_cache`` value to a view configuration, the
``Expires`` and ``Cache-Control`` headers of a response generated by the
associated view callable are modified. The value for ``http_cache`` may be
one of the following:
- A nonzero integer. If it's a nonzero integer, it's treated as a number
of seconds. This number of seconds will be used to compute the
``Expires`` header and the ``Cache-Control: max-age`` parameter of
responses to requests which call this view. For example:
``http_cache=3600`` instructs the requesting browser to 'cache this
response for an hour, please'.
- A ``datetime.timedelta`` instance. If it's a ``datetime.timedelta``
instance, it will be converted into a number of seconds, and that number
of seconds will be used to compute the ``Expires`` header and the
``Cache-Control: max-age`` parameter of responses to requests which call
this view. For example: ``http_cache=datetime.timedelta(days=1)``
instructs the requesting browser to 'cache this response for a day,
please'.
- Zero (``0``). If the value is zero, the ``Cache-Control`` and
``Expires`` headers present in all responses from this view will be
composed such that client browser cache (and any intermediate caches) are
instructed to never cache the response.
- A two-tuple. If it's a two tuple (e.g. ``http_cache=(1,
{'public':True})``), the first value in the tuple may be a nonzero
integer or a ``datetime.timedelta`` instance; in either case this value
will be used as the number of seconds to cache the response. The second
value in the tuple must be a dictionary. The values present in the
dictionary will be used as input to the ``Cache-Control`` response
header. For example: ``http_cache=(3600, {'public':True})`` means 'cache
for an hour, and add ``public`` to the Cache-Control header of the
response'. All keys and values supported by the
``webob.cachecontrol.CacheControl`` interface may be added to the
dictionary. Supplying ``{'public':True}`` is equivalent to calling
``response.cache_control.public = True``.
Providing a non-tuple value as ``http_cache`` is equivalent to calling
``response.cache_expires(value)`` within your view's body.
Providing a two-tuple value as ``http_cache`` is equivalent to calling
``response.cache_expires(value[0], **value[1])`` within your view's body.
If you wish to avoid influencing, the ``Expires`` header, and instead wish
to only influence ``Cache-Control`` headers, pass a tuple as ``http_cache``
with the first element of ``None``, e.g.: ``(None, {'public':True})``.
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