Source code for datalogd.plugins.csv_datafilter

from datalogd import DataFilter, listify

class CSVDataFilter(DataFilter):
    """
    Format received data into a table of comma separated values.

    The column headers can be formatted using values from the data. For example, for the data::

        [
            {'type': 'temperature', 'id': '0', 'value': 22.35},
            {'type': 'humidity', 'id': '0', 'value': 55.0},
            {'type': 'temperature', 'id': '1', 'value': 25.80},
        ]

    and a node initialised using::

        sink [class=CSVDataSink keys="['value']", labels="['{type}_{id}'"];

    the output will be::

        temperature_0,humidity_0,temperature_1
        22.35,55.0,25.80

    Setting ``labels`` to ``None`` will disable the column headers.

    By default, the column headers will be generated on every receipt of data. To instead output the
    column headers only once on the first receipt of data, use the parameter ``header="once"``.
    Setting ``header=None`` will also disable the headers completely.

    :param keys: Name of data keys to format into columns of the CSV.
    :param labels: Labels for the column headers, which may contain mappings to data values.
    :param header: Display the column header ``"once"`` or ``"every"`` or ``None``.
    """

    def __init__(self, sinks=[], keys=["timestamp", "value"], labels=["timestamp", "{type}_{id}"], header="every"):
        super().__init__(sinks=sinks)
        self.keys = keys
        self.labels = labels
        self._generate_header = header

    def receive(self, data):
        """
        Accept ``data`` and format into a table of CSV.

        :param data: Data to format as CSV.
        """
        data = listify(data)
        # Generate column headers
        col_labels = []
        cols = []
        for d in data:
            if self.keys and isinstance(d, dict):
                # May be inefficient, but orders keys as requested
                for k_i, k in enumerate(self.keys):
                    for dk in d.keys():
                        if k == dk:
                            if self.labels:
                                col_labels.append(self.labels[k_i].format_map(d))
                            cols.append(listify(d[k]))
            else:
                if self.labels: col_labels.append("data")
                cols.append(d)
        if len(data) > 0:
            csv = ""
            if self._generate_header in ("once", "every"):
                # Generate column header
                if self.labels: csv += ",".join(col_labels) + "\n"
            if self._generate_header == "once":
                # Generate header once on first data receipt
                self._generate_header = None
            # Generate row from data
            for r_i in range(min(len(x) for x in cols)):
                csv += ",".join([str(col[r_i]) for col in cols]) + "\n"
            self.send(csv.rstrip("\n"))