update from Atlas with major reorg
This commit is contained in:
Luciano Ramalho
84
21-class-metaprog/bulkfood/bulkfood_v6.py
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84
21-class-metaprog/bulkfood/bulkfood_v6.py
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"""
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A line item for a bulk food order has description, weight and price fields::
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>>> raisins = LineItem('Golden raisins', 10, 6.95)
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>>> raisins.weight, raisins.description, raisins.price
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(10, 'Golden raisins', 6.95)
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A ``subtotal`` method gives the total price for that line item::
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>>> raisins.subtotal()
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69.5
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The weight of a ``LineItem`` must be greater than 0::
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>>> raisins.weight = -20
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Traceback (most recent call last):
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...
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ValueError: value must be > 0
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No change was made::
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>>> raisins.weight
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10
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The value of the attributes managed by the descriptors are stored in
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alternate attributes, created by the descriptors in each ``LineItem``
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instance::
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# BEGIN LINEITEM_V6_DEMO
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>>> raisins = LineItem('Golden raisins', 10, 6.95)
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>>> dir(raisins)[:3]
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['_NonBlank#description', '_Quantity#price', '_Quantity#weight']
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>>> LineItem.description.storage_name
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'_NonBlank#description'
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>>> raisins.description
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'Golden raisins'
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>>> getattr(raisins, '_NonBlank#description')
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'Golden raisins'
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# END LINEITEM_V6_DEMO
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If the descriptor is accessed in the class, the descriptor object is
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returned:
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>>> LineItem.weight # doctest: +ELLIPSIS
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<model_v6.Quantity object at 0x...>
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>>> LineItem.weight.storage_name
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'_Quantity#weight'
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The `NonBlank` descriptor prevents empty or blank strings to be used
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for the description:
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>>> br_nuts = LineItem('Brazil Nuts', 10, 34.95)
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>>> br_nuts.description = ' '
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Traceback (most recent call last):
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...
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ValueError: value cannot be empty or blank
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>>> void = LineItem('', 1, 1)
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Traceback (most recent call last):
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...
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ValueError: value cannot be empty or blank
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"""
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# BEGIN LINEITEM_V6
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import model_v6 as model
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@model.entity # <1>
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class LineItem:
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description = model.NonBlank()
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weight = model.Quantity()
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price = model.Quantity()
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def __init__(self, description, weight, price):
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self.description = description
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self.weight = weight
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self.price = price
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def subtotal(self):
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return self.weight * self.price
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# END LINEITEM_V6
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79
21-class-metaprog/bulkfood/bulkfood_v7.py
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79
21-class-metaprog/bulkfood/bulkfood_v7.py
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@@ -0,0 +1,79 @@
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"""
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A line item for a bulk food order has description, weight and price fields::
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>>> raisins = LineItem('Golden raisins', 10, 6.95)
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>>> raisins.weight, raisins.description, raisins.price
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(10, 'Golden raisins', 6.95)
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A ``subtotal`` method gives the total price for that line item::
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>>> raisins.subtotal()
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69.5
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The weight of a ``LineItem`` must be greater than 0::
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>>> raisins.weight = -20
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Traceback (most recent call last):
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...
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ValueError: value must be > 0
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No change was made::
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>>> raisins.weight
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10
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The value of the attributes managed by the descriptors are stored in
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alternate attributes, created by the descriptors in each ``LineItem``
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instance::
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>>> raisins = LineItem('Golden raisins', 10, 6.95)
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>>> dir(raisins)[:3]
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['_NonBlank#description', '_Quantity#price', '_Quantity#weight']
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>>> LineItem.description.storage_name
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'_NonBlank#description'
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>>> raisins.description
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'Golden raisins'
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>>> getattr(raisins, '_NonBlank#description')
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'Golden raisins'
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If the descriptor is accessed in the class, the descriptor object is
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returned:
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>>> LineItem.weight # doctest: +ELLIPSIS
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<model_v7.Quantity object at 0x...>
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>>> LineItem.weight.storage_name
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'_Quantity#weight'
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The `NonBlank` descriptor prevents empty or blank strings to be used
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for the description:
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>>> br_nuts = LineItem('Brazil Nuts', 10, 34.95)
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>>> br_nuts.description = ' '
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Traceback (most recent call last):
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...
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ValueError: value cannot be empty or blank
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>>> void = LineItem('', 1, 1)
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Traceback (most recent call last):
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...
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ValueError: value cannot be empty or blank
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"""
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# BEGIN LINEITEM_V7
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import model_v7 as model
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class LineItem(model.Entity): # <1>
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description = model.NonBlank()
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weight = model.Quantity()
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price = model.Quantity()
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def __init__(self, description, weight, price):
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self.description = description
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self.weight = weight
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self.price = price
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def subtotal(self):
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return self.weight * self.price
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# END LINEITEM_V7
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86
21-class-metaprog/bulkfood/bulkfood_v8.py
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86
21-class-metaprog/bulkfood/bulkfood_v8.py
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@@ -0,0 +1,86 @@
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"""
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A line item for a bulk food order has description, weight and price fields::
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>>> raisins = LineItem('Golden raisins', 10, 6.95)
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>>> raisins.weight, raisins.description, raisins.price
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(10, 'Golden raisins', 6.95)
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A ``subtotal`` method gives the total price for that line item::
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>>> raisins.subtotal()
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69.5
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The weight of a ``LineItem`` must be greater than 0::
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>>> raisins.weight = -20
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Traceback (most recent call last):
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...
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ValueError: value must be > 0
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No change was made::
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>>> raisins.weight
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10
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>>> raisins = LineItem('Golden raisins', 10, 6.95)
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>>> dir(raisins)[:3]
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['_NonBlank#description', '_Quantity#price', '_Quantity#weight']
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>>> LineItem.description.storage_name
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'_NonBlank#description'
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>>> raisins.description
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'Golden raisins'
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>>> getattr(raisins, '_NonBlank#description')
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'Golden raisins'
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If the descriptor is accessed in the class, the descriptor object is
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returned:
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>>> LineItem.weight # doctest: +ELLIPSIS
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<model_v8.Quantity object at 0x...>
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>>> LineItem.weight.storage_name
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'_Quantity#weight'
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The `NonBlank` descriptor prevents empty or blank strings to be used
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for the description:
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>>> br_nuts = LineItem('Brazil Nuts', 10, 34.95)
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>>> br_nuts.description = ' '
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Traceback (most recent call last):
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...
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ValueError: value cannot be empty or blank
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>>> void = LineItem('', 1, 1)
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Traceback (most recent call last):
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...
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ValueError: value cannot be empty or blank
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Fields can be retrieved in the order they were declared:
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# BEGIN LINEITEM_V8_DEMO
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>>> for name in LineItem.field_names():
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... print(name)
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...
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description
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weight
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price
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# END LINEITEM_V8_DEMO
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"""
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import model_v8 as model
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class LineItem(model.Entity):
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description = model.NonBlank()
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weight = model.Quantity()
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price = model.Quantity()
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def __init__(self, description, weight, price):
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self.description = description
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self.weight = weight
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self.price = price
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def subtotal(self):
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return self.weight * self.price
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60
21-class-metaprog/bulkfood/model_v6.py
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60
21-class-metaprog/bulkfood/model_v6.py
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@@ -0,0 +1,60 @@
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import abc
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class AutoStorage:
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__counter = 0
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def __init__(self):
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cls = self.__class__
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prefix = cls.__name__
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index = cls.__counter
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self.storage_name = '_{}#{}'.format(prefix, index)
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cls.__counter += 1
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def __get__(self, instance, owner):
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if instance is None:
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return self
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else:
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return getattr(instance, self.storage_name)
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def __set__(self, instance, value):
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setattr(instance, self.storage_name, value)
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class Validated(abc.ABC, AutoStorage):
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def __set__(self, instance, value):
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value = self.validate(instance, value)
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super().__set__(instance, value)
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@abc.abstractmethod
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def validate(self, instance, value):
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"""return validated value or raise ValueError"""
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class Quantity(Validated):
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"""a number greater than zero"""
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def validate(self, instance, value):
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if value <= 0:
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raise ValueError('value must be > 0')
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return value
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class NonBlank(Validated):
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"""a string with at least one non-space character"""
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def validate(self, instance, value):
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value = value.strip()
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if len(value) == 0:
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raise ValueError('value cannot be empty or blank')
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return value
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# BEGIN MODEL_V6
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def entity(cls): # <1>
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for key, attr in cls.__dict__.items(): # <2>
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if isinstance(attr, Validated): # <3>
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type_name = type(attr).__name__
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attr.storage_name = '_{}#{}'.format(type_name, key) # <4>
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return cls # <5>
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# END MODEL_V6
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66
21-class-metaprog/bulkfood/model_v7.py
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66
21-class-metaprog/bulkfood/model_v7.py
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@@ -0,0 +1,66 @@
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import abc
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class AutoStorage:
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__counter = 0
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def __init__(self):
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cls = self.__class__
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prefix = cls.__name__
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index = cls.__counter
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self.storage_name = '_{}#{}'.format(prefix, index)
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cls.__counter += 1
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def __get__(self, instance, owner):
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if instance is None:
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return self
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else:
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return getattr(instance, self.storage_name)
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def __set__(self, instance, value):
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setattr(instance, self.storage_name, value)
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class Validated(abc.ABC, AutoStorage):
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def __set__(self, instance, value):
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value = self.validate(instance, value)
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super().__set__(instance, value)
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@abc.abstractmethod
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def validate(self, instance, value):
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"""return validated value or raise ValueError"""
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class Quantity(Validated):
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"""a number greater than zero"""
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def validate(self, instance, value):
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if value <= 0:
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raise ValueError('value must be > 0')
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return value
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class NonBlank(Validated):
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"""a string with at least one non-space character"""
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def validate(self, instance, value):
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value = value.strip()
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if len(value) == 0:
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raise ValueError('value cannot be empty or blank')
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return value
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# BEGIN MODEL_V7
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class EntityMeta(type):
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"""Metaclass for business entities with validated fields"""
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def __init__(cls, name, bases, attr_dict):
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super().__init__(name, bases, attr_dict) # <1>
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for key, attr in attr_dict.items(): # <2>
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if isinstance(attr, Validated):
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type_name = type(attr).__name__
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attr.storage_name = '_{}#{}'.format(type_name, key)
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class Entity(metaclass=EntityMeta): # <3>
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"""Business entity with validated fields"""
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# END MODEL_V7
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80
21-class-metaprog/bulkfood/model_v8.py
Normal file
80
21-class-metaprog/bulkfood/model_v8.py
Normal file
@@ -0,0 +1,80 @@
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import abc
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import collections
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class AutoStorage:
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__counter = 0
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def __init__(self):
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cls = self.__class__
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prefix = cls.__name__
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index = cls.__counter
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self.storage_name = '_{}#{}'.format(prefix, index)
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cls.__counter += 1
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def __get__(self, instance, owner):
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if instance is None:
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return self
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else:
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return getattr(instance, self.storage_name)
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def __set__(self, instance, value):
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setattr(instance, self.storage_name, value)
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class Validated(abc.ABC, AutoStorage):
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def __set__(self, instance, value):
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value = self.validate(instance, value)
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super().__set__(instance, value)
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@abc.abstractmethod
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def validate(self, instance, value):
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"""return validated value or raise ValueError"""
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class Quantity(Validated):
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"""a number greater than zero"""
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def validate(self, instance, value):
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if value <= 0:
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raise ValueError('value must be > 0')
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return value
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class NonBlank(Validated):
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"""a string with at least one non-space character"""
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def validate(self, instance, value):
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value = value.strip()
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if len(value) == 0:
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raise ValueError('value cannot be empty or blank')
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return value
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# BEGIN MODEL_V8
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class EntityMeta(type):
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"""Metaclass for business entities with validated fields"""
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@classmethod
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def __prepare__(cls, name, bases):
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return collections.OrderedDict() # <1>
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def __init__(cls, name, bases, attr_dict):
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super().__init__(name, bases, attr_dict)
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cls._field_names = [] # <2>
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for key, attr in attr_dict.items(): # <3>
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if isinstance(attr, Validated):
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type_name = type(attr).__name__
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attr.storage_name = '_{}#{}'.format(type_name, key)
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cls._field_names.append(key) # <4>
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class Entity(metaclass=EntityMeta):
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"""Business entity with validated fields"""
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@classmethod
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def field_names(cls): # <5>
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for name in cls._field_names:
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yield name
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# END MODEL_V8
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Block a user