Zero-dependency Logger class for logging of table-structured data in Python.

logger.py

class Logger:
    """Logger provides logging of table-structured data.
    The first column provided must be interpretable as a title. You may provide
    a 'formatting function' for each column that formats values corresponding
    to that column.

    >>> logger = Logger({
    ...     'Film Title': None,
    ...     'Running Time': lambda x: '{} hours'.format(round(x, 2)),
    ...     'Rating': lambda x: '⭐️' * x,
    ... }, csv=True)
    Film Title,Running Time,Rating
    >>> logger.log(['The Party', 5.6524, 4])
    The Party,5.65 hours,⭐️⭐️⭐️⭐️
    >>> logger.log(['Dracula', 2.345, 5], apply_funcs=False)
    Dracula,2.345,5
    """

    def __init__(self, columns, file=None, csv=False):
        assert len(columns) > 0
        self.file = file
        self.csv = csv
        self.set_columns(columns)

    def set_columns(self, columns):
        self.columns = list(columns.keys())
        self.funcs = list(columns.values())
        if self.csv:
            self._log_csv(self.columns)

    def set_output(self, file):
        self.file = file

    def _print(self, *args, **kwargs):
        print(*args, **kwargs, file=self.file)

    def _log_csv(self, row):
        self._print(','.join(row))

    def _log_pretty(self, row):
        row_title = ' '.join([self.columns[0], row[0]])
        self._print(row_title + '\n' + '=' * len(row_title))
        for column, item in zip(self.columns[1:], row[1:]):
            self._print(column + ':', item)
        self._print()

    def log(self, row, apply_funcs=True):
        # apply user-supplied functions to current input
        # and convert everything to a string for final logging
        if apply_funcs:
            row = [f(item) if f is not None else item
                   for item, f in zip(row, self.funcs)]
        row = [str(item) for item in row]

        # choose appropriate log function
        if self.csv:
            self._log_csv(row)
        else:
            self._log_pretty(row)