Simple Memory Backend

class cachelib.simple.SimpleCache(threshold=500, default_timeout=300, ignore_delete_many_errors=True)

Bases: BaseCache

Simple memory cache for single process environments. All operations are protected by a threading.RLock, making a cache instance safe to use from multiple threads within the same process.

Parameters:

• threshold (int) – the maximum number of items the cache stores before it starts deleting some.

• default_timeout (int | timedelta) –

  the default timeout that is used if no timeout is specified on set(). Either a number of seconds or a datetime.timedelta. A timeout of 0 indicates that the cache never expires.

  Changed in version 0.17.0: Accepts a datetime.timedelta.

• ignore_delete_many_errors (bool) –

  If False, delete_many() will raise a RuntimeError if any key fails to delete. Keys that do not exist are considered successfully deleted and do not raise.

  Changelog

  Added in version 0.16.0.

serializer = <cachelib.serializers.SimpleSerializer object>

get(key)

Look up key in the cache and return the value for it.

Parameters:

key (str) – the key to be looked up.

Returns:

The value if it exists and is readable, else None.

Return type:

Any

set(key, value, timeout=None)

Add a new key/value to the cache (overwrites value, if key already exists in the cache).

Parameters:

• key (str) – the key to set

• value (Any) – the value for the key

• timeout (int | timedelta | None) – the cache timeout for the key, either a number of seconds or a datetime.timedelta (if not specified, it uses the default timeout). A timeout of 0 indicates that the cache never expires.

Returns:

True if key has been updated, False for backend errors. Pickling errors, however, will raise a subclass of pickle.PickleError.

Return type:

bool | None

add(key, value, timeout=None)

Works like set() but does not overwrite the values of already existing keys.

Parameters:

• key (str) – the key to set

• value (Any) – the value for the key

• timeout (int | timedelta | None) – the cache timeout for the key, either a number of seconds or a datetime.timedelta (if not specified, it uses the default timeout). A timeout of 0 indicates that the cache never expires.

Returns:

Same as set(), but also False for already existing keys.

Return type:

bool

delete(key)

Delete key from the cache.

Parameters:

key (str) – the key to delete.

Returns:

Whether the key existed and has been deleted.

Return type:

bool

has(key)

Checks if a key exists in the cache without returning it. This is a cheap operation that bypasses loading the actual data on the backend.

Parameters:

key (str) – the key to check

Return type:

bool

clear()

Clears the cache. Keep in mind that not all caches support completely clearing the cache.

Returns:

Whether the cache has been cleared.

Return type:

bool

inc(key, delta=1)

Increments the value of a key by delta. If the key does not yet exist it is initialized with delta.

For supporting caches this is an atomic operation.

Parameters:

• key (str) – the key to increment.

• delta (int) – the delta to add.

Returns:

The new value or None for backend errors.

Return type:

int | None

dec(key, delta=1)

Decrements the value of a key by delta. If the key does not yet exist it is initialized with -delta.

For supporting caches this is an atomic operation.

Parameters:

• key (str) – the key to increment.

• delta (int) – the delta to subtract.

Returns:

The new value or None for backend errors.

Return type:

int | None