Keyword

class Cauldron.local.dispatcher.Keyword

Bases: Cauldron.base.dispatcher.Keyword

A dispatcher-based keyword, which should own its own values.

Attributes Summary

full_name	Full name.
name	Keyword name.
service
value	Map .value to ._last_value, the cauldron internal location of this variable.

Methods Summary

callback(function[, remove])	Register a function to be called whenever this keyword is set to a new value.
check(value)	Check that ‘value’ is appropriate for this keyword.
modify(value)	Modify this keyword’s value.
period(period)	How often a keyword should be updated.
postread(value)	Take some action post-read.
postwrite(value)	Take some action post-write.
preread()	Take some action before this value is read.
prewrite(value)	Any actions which need to occur before a value is written.
read()	Read the value from the authority source.
schedule([appointment, cancel])	Schedule an update.
set(value[, force])	Set the keyword to the value provided, and broadcast changes.
translate(value)	Translate a value into a standard representation.
update()	Update the value by performing a read.
write(value)	Write the value to the authority source.

Attributes Documentation

full_name

Full name. Includes Keyword and Service name.

name

Keyword name.

service = None

value

Map .value to ._last_value, the cauldron internal location of this variable.

Methods Documentation

callback(function, remove=False)

Register a function to be called whenever this keyword is set to a new value.

check(value)

Check that ‘value’ is appropriate for this keyword. If it is not, raise a value error.

This method can be overridden to provide specific behavior in user subclasses.

modify(value)

Modify this keyword’s value. This is the public function which should be called to change a keyword value.

period(period)

How often a keyword should be updated.

Note

Cauldron backends are not required to implement this function. If the do not, it will raise an CauldronAPINotImplemented error.

postread(value)

Take some action post-read. Called at the end of update().

This method can be overridden to provide specific behavior in user subclasses.

postwrite(value)

Take some action post-write.

This method can be overridden to provide specific behavior in user subclasses.

preread()

Take some action before this value is read. Called at the start of update().

This method can be overridden to provide specific behavior in user subclasses.

prewrite(value)

Any actions which need to occur before a value is written. Called to adjust the value in modify().

This can raise NoWriteNecessary if a write is not necessary.

This method can be overridden to provide specific behavior in user subclasses.

read()

Read the value from the authority source. Called to get the value for update().

This method can be overridden to provide specific behavior in user subclasses.

schedule(appointment=None, cancel=False)

Schedule an update.

Note

Cauldron backends are not required to implement this function. If the do not, it will raise an CauldronAPINotImplemented error.

set(value, force=False)

Set the keyword to the value provided, and broadcast changes.

Parameters:

• value – The keyword value.
• force (bool) – Whether to force the change, or ignore repeatedly setting a keyword to the same value.

translate(value)

Translate a value into a standard representation.

For e.g. an enumerated keyword, this should return the ascii representation of the underlying integer.

This method can be overridden to provide specific behavior in user subclasses.

update()

Update the value by performing a read. This is the public function which should be called when the keyword is read.

write(value)

Write the value to the authority source. Called to adjust the value in modify().

This method can be overridden to provide specific behavior in user subclasses.