====Session:Callback====

This function is part of the [[Session|Session]] class.

**Callback** is used to set the callback function you want to call when changes are made to your data.

While each of your [[Channel|Channels]] are automatically updated with new data as it comes in, callbacks provide a mechanism of knowing //when// those changes have occurred. 

===Parameters===

^Name^Description^
|Func|The Python callback function|

===Return Value===

No Return Value

===Callback Format===

Your callback function must take a single parameter - an array of each of the Channels that have been updated.

For example...

<code>
def MyCallback(updates):
   print("Value Changed: " + updates[0].AsText())
</code>
</code>