138 lines
2.8 KiB
Markdown
138 lines
2.8 KiB
Markdown
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# Exercise 9.3 - Solution
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## (a) Controlling Exported Symbols
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```python
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# structure.py
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__all__ = ['Structure']
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...
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```
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```python
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# reader.py
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__all__ = [ 'read_csv_as_dicts',
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'read_csv_as_instances' ]
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...
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```
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```python
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# tableformat.py
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__all__ = ['create_formatter', 'print_table']
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...
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```
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## (b) Exporting Everything
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```python
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# structly/__init__.py
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from .structure import *
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from .reader import *
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from .tableformat import *
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__all__ = [ *structure.__all__,
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*reader.__all__,
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*tableformat.__all__ ]
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```
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## (c) Module Splitting
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There are a few parts to this. First, the individual files in `tableformat/formats` are going to
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look like this:
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```python
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# tableformat/formats/text.py
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from ..formatter import TableFormatter
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class TextTableFormatter(TableFormatter):
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...
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# tableformat/formats/csv.py
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from ..formatter import TableFormatter
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class CSVTableFormatter(TableFormatter):
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...
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# tableformat/formats/html.py
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from ..formatter import TableFormatter
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class HTMLTableFormatter(TableFormatter):
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...
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```
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The `formatter.py` file will look like this:
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```python
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# tableformat/formatter.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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@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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from .formats.text import TextTableFormatter
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from .formats.csv import CSVTableFormatter
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from .formats.html import HTMLTableFormatter
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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 == 'text':
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formatter_cls = TextTableFormatter
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elif name == 'csv':
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formatter_cls = CSVTableFormatter
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elif name == 'html':
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formatter_cls = HTMLTableFormatter
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else:
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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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Finally, you need to have a `tableformat/__init__.py` file like this:
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```python
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# tableformat/__init__.py
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from .formatter import print_table, create_formatter
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__all__ = [ 'print_table', 'create_formatter' ]
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```
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[Back](ex9_3.md)
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