platypush/platypush/plugins/variable.py

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from platypush.config import Config
from platypush.context import get_plugin
from platypush.plugins import Plugin, action
class VariablePlugin(Plugin):
"""
This plugin allows you to manipulate context variables that can be
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accessed across your tasks. It requires the :mod:`platypush.plugins.db`
plugin to be enabled, as the variables will be stored on a local database
for persistency and multi-process sharing purposes.
Requires:
* **sqlalchemy** (``pip install sqlalchemy``)
"""
_variable_table_name = 'variable'
def __init__(self, *args, **kwargs):
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"""
The plugin will create a table named ``variable`` on the database
configured in the :mod:`platypush.plugins.db` plugin. You'll have
to specify a default ``engine`` in your ``db`` plugin configuration.
"""
super().__init__(*args, **kwargs)
self.db_plugin = get_plugin('db')
db = Config.get('db')
self.db_config = {
'engine': db.get('engine'),
'args': db.get('args', []),
'kwargs': db.get('kwargs', {})
}
self._create_tables()
# self._variables = {}
def _create_tables(self):
self.db_plugin.execute("""CREATE TABLE IF NOT EXISTS {}(
name varchar(255) not null primary key,
value text
)""".format(self._variable_table_name))
@action
def get(self, name, default_value=None):
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"""
Get the value of a variable by name.
:param name: Variable name
:type name: str
:param default_value: What will be returned if the variable is not defined (default: None)
:returns: A map in the format ``{"<name>":"<value>"}``
"""
rows = self.db_plugin.select(table=self._variable_table_name,
filter={'name': name},
engine=self.db_config['engine'],
*self.db_config['args'],
**self.db_config['kwargs']).output
return {name: rows[0]['value'] if rows else None}
@action
def set(self, **kwargs):
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"""
Set a variable or a set of variables.
:param kwargs: Key-value list of variables to set (e.g. ``foo='bar', answer=42``)
"""
records = [ { 'name': k, 'value': v }
for (k,v) in kwargs.items() ]
self.db_plugin.insert(table=self._variable_table_name,
records=records, key_columns=['name'],
engine=self.db_config['engine'],
on_duplicate_update=True,
*self.db_config['args'],
**self.db_config['kwargs'])
return kwargs
@action
def unset(self, name):
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"""
Unset a variable by name if it's set
:param name: Name of the variable to remove
:type name: str
"""
records = [ { 'name': name } ]
self.db_plugin.delete(table=self._variable_table_name,
records=records, engine=self.db_config['engine'],
*self.db_config['args'],
**self.db_config['kwargs'])
return True
# vim:sw=4:ts=4:et: