摘自謬雪峰
>>> s = student()
>>> s.name = 'michael' # 動態給例項繫結乙個屬性
>>> def set_age(self, age): # 定義乙個函式作為例項方法
... self.age = age
...>>> from types import methodtype
>>> s.set_age = methodtype(set_age, s) # 給例項繫結乙個方法
>>> s.set_age(25) # 呼叫例項方法
>>> s.age # 測試結果
25
>>> def set_score(self, score):
... self.score = score
...>>> student.set_score = set_score
為了達到限制的目的，python允許在定義class的時候，定義乙個特殊的__slots__變數，來限制該class例項能新增的屬性：
class student(object):
__slots__ = ('name', 'age') # 用tuple定義允許繫結的屬性名稱
>>> s.score = 99 # 繫結屬性'score'
traceback (most recent call last):
file "", line 1, in attributeerror: 'student' object has no attribute 'score'
使用__slots__要注意，__slots__定義的屬性僅對當前類例項起作用，對繼承的子類是不起作用的：class graduatestudent(student):
... pass
...g = graduatestudent()
g.score = 9999
除非在子類中也定義__slots__，這樣，子類例項允許定義的屬性就是自身的__slots__加上父類的__slots__。
@property用來在類中定義規則，並且外部簡單呼叫，即外部例項話後，不用呼叫方法來設定屬性，而是直接設定屬性
class student(object):
@property
def score(self):
return self._score
@score.setter # 沒有score.setter則該屬性為唯讀屬性
def score(self, value):
if not isinstance(value, int):
raise valueerror('score must be an integer!')
if value < 0 or value > 100:
raise valueerror('score must between 0 ~ 100!')
self._score = value
>>> s = student()
>>> s.score = 60 # ok，實際轉化為s.set_score(60)
>>> s.score # ok，實際轉化為s.get_score()
60>>> s.score = 9999
traceback (most recent call last):
...valueerror: score must between 0 ~ 100!
pass
只有在沒有找到屬性的情況下，才呼叫__getattr__，已有的屬性，比如name，不會在__getattr__中查詢。
class student(object):
def __init__(self):
self.name = 'michael'
def __getattr__(self, attr):
if attr=='score':
return 99
else:
raise attributeerror('\'student\' object has no attribute \'%s\'' % attr)
definit(self, name):
self.name = name
def __call__(self):
print('my name is %s.' % self.name)
s = student('michael')s() # self引數不要傳入
my name is michael.
通過callable()函式，我們就可以判斷乙個物件是否是「可呼叫」物件。
callable(student())true
callable(max)
true
callable([1, 2, 3])
false
callable(none)
false
callable('str')
false
from enum import enum
month = enum('monster', ('jan', 'feb', 'mar', 'apr', 'may', 'jun', 'jul', 'aug', 'sep', 'oct', 'nov', 'dec'))
#類似於字典的鍵值對的形式
print(month.jan)#返回monster.jan
for name, member in month.__members__.items():
print(name, '=>', member, ',', member.value)
#結果如下
'''jan => monster.jan , 1
feb => monster.feb , 2
mar => monster.mar , 3
apr => monster.apr , 4
may => monster.may , 5
jun => monster.jun , 6
jul => monster.jul , 7
aug => monster.aug , 8
sep => monster.sep , 9
oct => monster.oct , 10
nov => monster.nov , 11'''
from enum import enum, unique
@unique
class weekday(enum):
sun = 0 # sun的value被設定為0
mon = 1
tue = 2
wed = 3
thu = 4
fri = 5
sat = 6
@unique裝飾器可以幫助我們檢查保證沒有重複值。
訪問這些列舉型別可以有若干種方法：
day1 = weekday.monprint(day1)
weekday.mon
print(weekday.tue)
weekday.tue
print(weekday['tue'])
weekday.tue
print(weekday.tue.value)
2print(day1 == weekday.mon)
true
print(day1 == weekday.tue)
false
print(weekday(1))
weekday.mon
print(day1 == weekday(1))
true
weekday(7)
traceback (most recent call last):
...valueerror: 7 is not a valid weekday
for name, member in weekday.members.items():
... print(name, '=>', member)
...sun => weekday.sun
mon => weekday.mon
tue => weekday.tue
wed => weekday.wed
thu => weekday.thu
fri => weekday.fri
sat => weekday.sat
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