Class Table

recipes/Python/577825_Rudimentary_Database_Engine/recipe-577825.py:321–722

Table(*columns) -> Table

################################################################################

class Table:

    "Table(*columns) -> Table"

    @classmethod
    def from_iter(cls, iterator):
        "Generates a table from a column / rows iterator."
        title, test_row, *rows = iterator
        table = cls(*zip(title, map(type, test_row)))
        table.insert(*test_row)
        for row in rows:
            table.insert(*row)
        return table

    ########################################################################

    __slots__ = _slots('columns data_area row_index')

    def __init__(self, *columns):
        "Initializes Table with columns and row storage area."
        self.__columns = _Columns(columns)
        self.__data_area = {}
        self.__row_index = 1

    def __len__(self):
        "Returns the number of rows in the table."
        return len(self.__data_area)

    def __repr__(self):
        "Creates a complete representation of the table."
        buffer = [list(map(repr, ['ROW_ID'] + [name for index, name, data_type \
                                               in self.__columns]))]
        width = [0] * len(buffer[0])
        for row in sorted(self.__data_area):
            buffer.append(list(map(repr, [row] + [self.__data_area[row][index] \
                                                  for index, name, data_type \
                                                  in self.__columns])))
        for row in buffer:
            for index, string in enumerate(row):
                width[index] = max(width[index], len(string))
        string = ''
        for index, value in enumerate(buffer[0]):
            string += value.ljust(width[index]) + ' | '
        string = string[:-3] + '\n'
        for index in range(len(buffer[0])):
            string += '-' * width[index] + '-+-'
        string = string[:-3] + '\n'
        for row in buffer[1:]:
            for index, value in enumerate(row):
                string += value.ljust(width[index]) + ' | '
            string = string[:-3] + '\n'
        return string[:-1]

    def __str__(self):
        names, *rows = self
        columns = {name: [] for name in names}
        for row in rows:
            for key, value in zip(names, row):