64 lines
1.4 KiB
Python
64 lines
1.4 KiB
Python
"""
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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 check is also performed on instantiation::
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>>> walnuts = LineItem('walnuts', 0, 10.00)
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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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The proteced attribute can still be accessed if needed for some reason, such as
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white box testing)::
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>>> raisins._LineItem__weight
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10
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"""
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# tag::LINEITEM_V2[]
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class LineItem:
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def __init__(self, description, weight, price):
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self.description = description
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self.weight = weight # <1>
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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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@property # <2>
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def weight(self): # <3>
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return self.__weight # <4>
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@weight.setter # <5>
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def weight(self, value):
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if value > 0:
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self.__weight = value # <6>
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else:
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raise ValueError('value must be > 0') # <7>
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# end::LINEITEM_V2[]
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