Caching¶

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When your application runs slow, throw some caches in. Well, at least -it’s the easiest way to speed up things. What does a cache do? Say you -have a function that takes some time to complete but the results would -still be good enough if they were 5 minutes old. So then the idea is that -you actually put the result of that calculation into a cache for some -time.

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Flask itself does not provide caching for you, but Werkzeug, one of the -libraries it is based on, has some very basic cache support. It supports -multiple cache backends, normally you want to use a memcached server.

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Setting up a Cache¶

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You create a cache object once and keep it around, similar to how -Flask objects are created. If you are using the -development server you can create a -SimpleCache object, that one is a simple -cache that keeps the item stored in the memory of the Python interpreter:

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from werkzeug.contrib.cache import SimpleCache
-cache = SimpleCache()
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If you want to use memcached, make sure to have one of the memcache modules -supported (you get them from PyPI) and a -memcached server running somewhere. This is how you connect to such an -memcached server then:

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from werkzeug.contrib.cache import MemcachedCache
-cache = MemcachedCache(['127.0.0.1:11211'])
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If you are using App Engine, you can connect to the App Engine memcache -server easily:

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from werkzeug.contrib.cache import GAEMemcachedCache
-cache = GAEMemcachedCache()
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Using a Cache¶

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Now how can one use such a cache? There are two very important -operations: get() and -set(). This is how to use them:

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To get an item from the cache call -get() with a string as key name. -If something is in the cache, it is returned. Otherwise that function -will return None:

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rv = cache.get('my-item')
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To add items to the cache, use the set() -method instead. The first argument is the key and the second the value -that should be set. Also a timeout can be provided after which the cache -will automatically remove item.

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Here a full example how this looks like normally:

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def get_my_item():
-    rv = cache.get('my-item')
-    if rv is None:
-        rv = calculate_value()
-        cache.set('my-item', rv, timeout=5 * 60)
-    return rv
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Caching¶

Setting up a Cache¶

Using a Cache¶

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Caching¶

Setting up a Cache¶

Using a Cache¶

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