soln3_8.md

Exercise 3.8 - Solution

# tableformat.py
from abc import ABC, abstractmethod

def print_table(records, fields, formatter):
    if not isinstance(formatter, TableFormatter):
        raise RuntimeError('Expected a TableFormatter')

    formatter.headings(fields)
    for r in records:
        rowdata = [getattr(r, fieldname) for fieldname in fields]
        formatter.row(rowdata)

class TableFormatter(ABC):
    @abstractmethod
    def headings(self, headers):
        pass

    @abstractmethod
    def row(self, rowdata):
        pass


class TextTableFormatter(TableFormatter):
    def headings(self, headers):
        print(' '.join('%10s' % h for h in headers))
        print(('-'*10 + ' ')*len(headers))
    
    def row(self, rowdata):
        print(' '.join('%10s' % d for d in rowdata))

class CSVTableFormatter(TableFormatter):
    def headings(self, headers):
        print(','.join(headers))

    def row(self, rowdata):
        print(','.join(str(d) for d in rowdata))

class HTMLTableFormatter(TableFormatter):
    def headings(self, headers):
        print('<tr>', end=' ')
        for h in headers:
            print('<th>%s</th>' % h, end=' ')
        print('</tr>')

    def row(self, rowdata):
        print('<tr>', end=' ')
        for d in rowdata:
            print('<td>%s</td>' % d, end=' ')
        print('</tr>')


class ColumnFormatMixin:
    formats = []
    def row(self, rowdata):
        rowdata = [ (fmt % item) for fmt, item in zip(self.formats, rowdata)]
        super().row(rowdata)

class UpperHeadersMixin:
    def headings(self, headers):
        super().headings([h.upper() for h in headers])

def create_formatter(name, column_formats=None, upper_headers=False):
    if name == 'text':
        formatter_cls = TextTableFormatter
    elif name == 'csv':
        formatter_cls = CSVTableFormatter
    elif name == 'html':
        formatter_cls = HTMLTableFormatter
    else:
        raise RuntimeError('Unknown format %s' % name)

    if column_formats:
        class formatter_cls(ColumnFormatMixin, formatter_cls):
              formats = column_formats

    if upper_headers:
        class formatter_cls(UpperHeadersMixin, formatter_cls):
            pass

    return formatter_cls()

Back