relay.py

import yaml
import numpy as np
import os

from theano import config


class relay(object):
    def __init__(self, switches, ymlfile, callevery=1):
        """
        Given the path to a YAML file (`ymlfile`) and a dictionary `switches` having the format
        {'name': theano-shared-variable, ...}, this class' read method sets the value of the theano shared variable
        with the one found in the corresponding field of the YAML file.

        :type ymlfile: str
        :param ymlfile: Path to YAML file where the parameters are stored.

        :type switches: dict
        :param switches: Should be {'name': sharedvar, ...}, where sharedvar is a theano shared variable and 'name' is
                         the corresponding access key in the YAML file.
        """

        # Meta
        self.switches = switches
        self.ymlfile = ymlfile
        self.lastmodified = 0.

    def read(self):
        # Check if there are changes to the read
        filehaschanged = os.stat(self.ymlfile).st_mtime != self.lastmodified
        # Update lastmodified timestamp
        if filehaschanged:
            self.lastmodified = os.stat(self.ymlfile).st_mtime
        else:
            return

        # Read from file
        with open(self.ymlfile, 'r') as f:
            update = yaml.load(f)

        # Update switches
        for switchname, switchvar in self.switches.items():
            # Fetch
            if switchname in update.keys():
                # Check if update needs to be eval-ed
                if isinstance(update[switchname], str) and update[switchname].startswith('np.'):
                    switchvarval = eval(update[switchname])
                else:
                    switchvarval = getattr(np, config.floatX)(update[switchname])
                # Set switch variable
                switchvar.set_value(switchvarval)
        return

    def __call__(self, *args, **kwargs):
        self.read()