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August 30, 2017 07:58
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# Simple (?) example of descriptor use in Python. | |
class FullName(): | |
def __get__(self, i, o): | |
return '%s %s' % (i.first_name, i.last_name) | |
class LastName(): | |
def __get__(self, i, o): | |
if i.married and i.gender == Person.female and i.spouse is not None: | |
return i.spouse.text_last_name | |
return i.text_last_name | |
class Person(): | |
male = 1 | |
female = 2 | |
last_name = LastName() | |
def __init__(self, first_name, last_name, gender, married, spouse): | |
self.first_name = first_name | |
self.text_last_name = last_name | |
self.gender = gender | |
self.married = married | |
self.spouse = spouse | |
if spouse is not None: | |
spouse.spouse = self | |
def marry(spouse): | |
# Let's assume same-sex marriage is cool. | |
# and people don't change surnames in a same-sex marriage. | |
self.married = True | |
self.spouse = spouse | |
# FIXME: This won't work in countries that support polygamy. | |
self.spouse.spouse = self | |
def divorce(): | |
self.married = False | |
# FIXME: This won't work in countries that support polygamy. | |
self.spouse.spouse = None | |
self.spouse = None | |
# In [163]: jd = Person("John", "Doe", Person.male, True, None) | |
# | |
# In [164]: jf = Person("Jane", "Fonda", Person.female, True, jd) | |
# | |
# In [165]: jf.name | |
# Out[165]: 'Jane Doe' | |
# | |
# In [166]: jf.divorce() | |
# | |
# In [167]: jf.name | |
# Out[167]: 'Jane Fonda' | |
# | |
# In [168]: jf.marry(jd) | |
# | |
# In [169]: jf.name | |
# Out[169]: 'Jane Doe' |
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