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Atomically decrements a key's value.
google.appengine.api.memcache.decr(
key, delta=1, namespace=None, initial_value=None
)
Internally, the value is a unsigned 64-bit integer. Memcache caps decrementing below zero to zero.
The key must already exist in the cache to be decremented. See
docs on incr()
for details.
Args | |
---|---|
key
|
Key to decrement. If an iterable collection, each one of the keys will be offset. See Client's docstring for details. |
delta
|
Non-negative integer value (int or long) to decrement key by, defaulting to 1. |
namespace
|
a string specifying an optional namespace to use in the request. |
initial_value
|
initial value to put in the cache, if it doesn't already exist. The default value, None, will not create a cache entry if it doesn't already exist. |
Returns | |
---|---|
If key was a single value, the new long integer value, or None if key
was not in the cache, could not be decremented for any other reason, or
a network/RPC/server error occurred.
If key was an iterable collection, a dictionary will be returned mapping supplied keys to values, with the values having the same meaning as the singular return value of this method. |
Raises | |
---|---|
ValueError
|
If number is negative. |
TypeError
|
If delta isn't an int or long. |