Add method to decorated function to allow precaching of results.

README.rst

@@ -93,7 +93,7 @@ The Cachier wrapper adds a ``clear_cache()`` function to each wrapped function.
 
   foo.clear_cache()
 
-Genereal Configuration
+General Configuration
 ----------------------
 
 Threads Limit
@@ -148,6 +148,24 @@ See here for an example:
 `Question: How to work with unhashable arguments <https://github.com/python-cachier/cachier/issues/91>`_
 
 
+Precaching values
+---------------------------------
+
+If you want to load a value into the cache without calling the underlying function, this can be done with the `precache_value` function.
+
+.. code-block:: python
+
+  @cachier()
+  def add(arg1, arg2):
+    return arg1 + arg2
+
+  foo.precache_value(2, 2, value_to_cache=5)
+
+  result = add(2, 2)
+  print(result)  # prints 5
+
+
+
 Per-function call arguments
 ---------------------------
 
@@ -381,5 +399,3 @@ Notable bugfixers:
 .. links:
 .. _pymongo: https://api.mongodb.com/python/current/
 .. _watchdog: https://github.com/gorakhargosh/watchdog
-
-

cachier/base_core.py

@@ -37,6 +37,12 @@ def get_entry(self, args, kwds):
         key = self.hash_func(args, kwds)
         return self.get_entry_by_key(key)
 
+    def precache_value(self, args, kwds, value_to_cache):
+        """Writes a precomputed value into the cache."""
+        key = self.hash_func(args, kwds)
+        self.set_entry(key, value_to_cache)
+        return value_to_cache
+
     @abc.abstractmethod
     def get_entry_by_key(self, key):
         """Returns the result mapped to the given key in this core's cache,

cachier/core.py

@@ -259,9 +259,20 @@ def cache_dpath():
             except AttributeError:
                 return None
 
+        def precache_value(*args, value_to_cache, **kwds):
+            """Add an initial value to the cache.
+
+            Arguments
+            ---------
+            value : any
+                entry to be written into the cache
+            """
+            return core.precache_value(args, kwds, value_to_cache)
+
         func_wrapper.clear_cache = clear_cache
         func_wrapper.clear_being_calculated = clear_being_calculated
         func_wrapper.cache_dpath = cache_dpath
+        func_wrapper.precache_value = precache_value
         return func_wrapper
 
     return _cachier_decorator

tests/test_general.py

@@ -141,3 +141,31 @@ def _calls_wait_for_calc_timeout_slow(res_queue):
     res4 = _wait_for_calc_timeout_slow(1, 2)
     # One of the cached values is returned
     assert res1 == res4 or res2 == res4 or res3 == res4
+
+
+@pytest.mark.parametrize(
+    'mongetter,backend',
+    [
+        (_test_mongetter, 'mongo'),
+        (None, 'memory'),
+        (None, 'pickle'),
+    ]
+)
+def test_precache_value(mongetter, backend):
+
+    @cachier(backend=backend, mongetter=mongetter)
+    def func(arg_1, arg_2):
+        """Some function."""
+        return arg_1 + arg_2
+
+    result = func.precache_value(2, 2, value_to_cache=5)
+    assert result == 5
+    result = func(2, 2)
+    assert result == 5
+    func.clear_cache()
+    result = func(2, 2)
+    assert result == 4
+    result = func.precache_value(2, arg_2=2, value_to_cache=5)
+    assert result == 5
+    result = func(2, arg_2=2)
+    assert result == 5