flexible_calculation_state.py

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#!/usr/bin/env python
from flexbe_core import EventState, Logger


class FlexibleCalculationState(EventState):
    '''
    Implements a state that can perform a calculation based on multiple userdata inputs
    provided as a list to the calculation function.

    -- calculation  function    The function that performs the desired calculation.
                                It could be a private function (self.foo) manually defined in a behavior's source code
                                or a lambda function (e.g., lambda x: x[0]^2 + x[1]^2).
    -- input_keys   string[]    List of available input keys.

    ># input_keys   object[]    Input(s) to the calculation function as a list of userdata.
                                The individual inputs can be accessed as list elements (see lambda expression example).

    #> output_value object      The result of the calculation.

    <= done                     Indicates completion of the calculation.
    '''

    def __init__(self, calculation, input_keys):
        super(FlexibleCalculationState, self).__init__(outcomes=['done'],
                                                       input_keys=input_keys,
                                                       output_keys=['output_value'])
        self._calculation = calculation
        self._calculation_result = None

    def execute(self, userdata):
        userdata.output_value = self._calculation_result
        # nothing to check
        return 'done'

    def on_enter(self, userdata):
        if self._calculation is not None:
            try:
                self._calculation_result = self._calculation(**{key: userdata[key] for key in self._input_keys})
            except Exception as e:
                Logger.logwarn('Failed to execute calculation function!\n%s' % str(e))
        else:
            Logger.logwarn('Passed no calculation!')