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在定義繼承類的時(shí)候，有幾點(diǎn)是需要注意的：

class Student()定義的時(shí)候，需要在括號(hào)內(nèi)寫明繼承的類Person

在__init__()方法，需要調(diào)用super(Student, self).__init__(name, gender)，來初始化從父類繼承過來的屬性

#!/usr/bin/env?python
#?coding:?utf-8
"""
@author???ChenDehua?2021/4/22?19:31
@note?????
"""
import?time
def?log(timeunit):

????def?wrapper(f):
????????def?inner_wrapper(*args,?**kwargs):
????????????print("current?timeunit?is?{}".format(timeunit))
????????????start?=?time.time()
????????????print("start?time?->?{}".format(start))
????????????result?=?f(*args,?**kwargs)
????????????time.sleep(1)
????????????end?=?time.time()
????????????print("end?time?->?{}?spend?time?:{}"
??????????????????.format(end,?end?-?start?if?timeunit?==?"s"?else?(end?*?1000)?-?(start?*?1000)))
????????????return?result

????????return?inner_wrapper
????return?wrapper


@log("ms")
def?register_student(name,age,**kwargs):
????print("register_student?-->?name:{}?age:{}?additional?info:{}"
??????????.format(name,?age,?"".join(["{}:{}??".format(key,?value)?for?key,value?in?kwargs.items()])))


if?__name__?==?"__main__":
????register_student("chendehua",?21,?class_no=1800502108,?school="gdpu")

print([item?for?item?in?sorted(['bob',?'about',?'Zoo',?'Credit'],?key=lambda?value:value[0].lower())])

一行代碼搞定

一行搞定：

print([item?for?item?in?filter(lambda?x:int(math.sqrt(x))?*?int(math.sqrt(x))==?x,?[i?for?i?in?range(1,100)])])

if?__name__?==?"__main__":
????with?open("file.txt",?'a+')?as?file:
????????file.seek(0)
????????lines?=?file.readlines()
????????file.write("\n")
????????for?line?in?lines:
????????????file.write(line)

if?__name__?==?"__main__":
????file?=?open("file.txt",?"r")
????line2?=?file.readlines()

????new_file?=?open("file1.txt",?'w')
????for?index,?line?in?enumerate(line2):

????????line?=?line[-2::-1]?if?index?!=?len(line2)?-?1?else?line[::-1]
????????new_file.write(line?+?"\n"?if?index?!=?len(line2)?-?1?else?line)

????new_file.close()
????file.close()

這才是正確答案

例子：運(yùn)行時(shí)導(dǎo)入上級(jí)目錄的模塊

if __name__ == "__main__":
? ?import sys
? ?sys.path.append("../")
? ?import hello
? ?hello.say_hello()

關(guān)于多重繼承，需要徹底弄懂！

有如下繼承關(guān)系：

class A:
? ?def __init__(self, msg):
? ? ? ?print("init A..", msg)

class B(A):
? ?def __init__(self, msg):
? ? ? ?super(B, self).__init__(msg)
? ? ? ?print("init B..", msg)

class C(A):
? ?def __init__(self, msg):
? ? ? ?super(C, self).__init__(msg)
? ? ? ?print("init C..", msg)

class D1(C):
? ?def __init__(self, msg):
? ? ? ?super(D1, self).__init__(msg)
? ? ? ?print("init D1..", msg)

class D(C,B):
? ?def __init__(self, msg):
? ? ? ?super(D, self).__init__(msg)
? ? ? ?print("init D..", msg)

class Zero:
? ?def __init__(self, msg):
? ? ? ?print("init Zero", msg)

class One(Zero):
? ?def __init__(self, msg):
? ? ? ?super(One, self).__init__(msg)
? ? ? ?print("init One", msg)

class E(One, C):
? ?def __init__(self):
? ? ? ?super(C, self).__init__("ddd")class E(One, C):
? ?def __init__(self):
? ? ? ?super(C, self).__init__("ddd")

super(C, self).__init__("ddd")的意思是找類C的父類（類A）

ddd作為類A的msg：

e = E()

只輸出init A.. ddd

如果是super(One, self).__init__("ddd")，代表找One的父類（Zero），輸出init Zero ddd(super(One,self)只是找One的父類，并不會(huì)執(zhí)行One的init方法)

如果是super(E, self).__init__("ddd"),則會(huì)輸出

init Zero ddd
init One ddd

找E的父類，此時(shí)因?yàn)镋是多重繼承，繼承了One，和C，此時(shí)super(E,self)就會(huì)選擇第一個(gè)類One,而不會(huì)去找C

還有一種情況就是菱形繼承：

class Base(object):
? ?def __init__(self):
? ? ? ?print("enter Base")
? ? ? ?print("leave Base")

class A(Base):
? ?def __init__(self):
? ? ? ?print("enter A")
? ? ? ?super(A, self).__init__()
? ? ? ?print("leave A")

class B(Base):
? ?def __init__(self):
? ? ? ?print("enter B")
? ? ? ?super(B, self).__init__()
? ? ? ?print("leave B")

class C(A, B):
? ?def __init__(self):
? ? ? ?print("enter C")
? ? ? ?super(C, self).__init__()
? ? ? ?print("leave C")

if __name__ == "__main__":
? ?c = C()

輸出：

enter C
enter A
enter B
enter Base
leave Base
leave B
leave A
leave C

看看c的mro就知道調(diào)用順序了

>>> C.mro() ? # or C.__mro__ or C().__class__.mro()
[__main__.C, __main__.A, __main__.B, __main__.Base, object]

不存在菱形繼承問題的時(shí)候（第一種情況），就可以手動(dòng)指定需要去調(diào)用哪一個(gè)類的父類，如果父類是多重繼承的，就取第一個(gè)類。

class A:
? ?def __init__(self, msg):
? ? ? ?print("init A..", msg)
class C(A):
? ?def __init__(self, msg):
? ? ? ?super(C, self).__init__(msg)
? ? ? ?print("init C..", msg)
class Zero:
? ?def __init__(self, msg):
? ? ? ?print("init Zero", msg)
class Zero1:
? ?def __init__(self, msg):
? ? ? ?print("init Zero1", msg)

class One(Zero, Zero1):
? ?def __init__(self, msg):
? ? ? ?super(One, self).__init__(msg)
? ? ? ?print("init One", msg)

class E(One, C):
? ?def __init__(self):
? ? ? ?# super(E, self).__init__("ddd")
? ? ? ?super(One, self).__init__("ddd")

if __name__ == "__main__":
? ?e = E()

所以，super可以調(diào)用多次，來選擇不同父類的init方法

第二種情況，菱形問題的時(shí)候，就需要用到mro，來決定調(diào)用順序

class Animal(object):

? ? def __init__(self, name, age):#初始化

? ? ? ? self.name=name

? ? ? ? self.age=age

dog=Animal("曦曦",10)

cat=Animal("歡歡",9)

print(dog.name,dog.age)

在定義繼承類的時(shí)候，有幾點(diǎn)是需要注意的：

class Student()定義的時(shí)候，需要在括號(hào)內(nèi)寫明繼承的類Person

在__init__()方法，需要調(diào)用super(Student, self).__init__(name, gender)，來初始化從父類繼承過來的屬性

在類屬性和實(shí)例屬性同時(shí)存在的情況下，實(shí)例屬性的優(yōu)先級(jí)是要高于類屬性的，在操作實(shí)例的時(shí)候，優(yōu)先是操作實(shí)例的屬性。

可見通過實(shí)例是無法修改類的屬性的，事實(shí)上，通過實(shí)例方法修改類屬性，只是給實(shí)例綁定了一個(gè)對(duì)應(yīng)的實(shí)例屬性。

r1 = Rational(1, 2) 第一個(gè)數(shù)是1/2

r2 = Rational(1, 5) 第二個(gè)數(shù)是1/5