64 lines
1.6 KiB
Markdown
64 lines
1.6 KiB
Markdown
# Exercise 9.4 - Solution
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```python
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# tableformat.py
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from abc import ABC, abstractmethod
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def print_table(records, fields, formatter):
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if not isinstance(formatter, TableFormatter):
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raise RuntimeError('Expected a TableFormatter')
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formatter.headings(fields)
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for r in records:
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rowdata = [getattr(r, fieldname) for fieldname in fields]
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formatter.row(rowdata)
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class TableFormatter(ABC):
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_formats = { }
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@classmethod
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def __init_subclass__(cls):
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name = cls.__module__.split('.')[-1]
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TableFormatter._formats[name] = cls
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@abstractmethod
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def headings(self, headers):
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pass
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@abstractmethod
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def row(self, rowdata):
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pass
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class ColumnFormatMixin:
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formats = []
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def row(self, rowdata):
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rowdata = [ (fmt % item) for fmt, item in zip(self.formats, rowdata)]
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super().row(rowdata)
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class UpperHeadersMixin:
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def headings(self, headers):
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super().headings([h.upper() for h in headers])
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def create_formatter(name, column_formats=None, upper_headers=False):
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if name not in TableFormatter._formats:
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__import__(f'{__package__}.formats.{name}')
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formatter_cls = TableFormatter._formats.get(name)
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if not formatter_cls:
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raise RuntimeError('Unknown format %s' % name)
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if column_formats:
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class formatter_cls(ColumnFormatMixin, formatter_cls):
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formats = column_formats
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if upper_headers:
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class formatter_cls(UpperHeadersMixin, formatter_cls):
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pass
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return formatter_cls()
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```
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[Back](ex9_4.md)
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