gistfile1.py

def modify_cache(cache, key, timeout, callback):
    """
    A abstraction from the common, cache.get, if None, cache.set pattern.

    Test an uncached value:
    >>> cache = __mock_cache(None)
    >>> modify_cache(cache, 'foo', 1000, lambda: 1)
    1
    >>> cache.get.assert_called_with('foo')
    >>> cache.set.assert_called_with('foo', 1, 1000)

    Test a cached value:

    >>> cache = __mock_cache(1)
    >>> modify_cache(cache, 'bar', 1000, lambda: 2)
    1
    >>> cache.get.assert_called_with('bar')
    >>> cache.set.called
    False
    """
    ret = cache.get(key)
    if ret is None:
        ret = callback()
        cache.set(key, ret, timeout)
        
    return ret