[Python]重载运算符

Python运算符重载

MethodOverloadsCall for__init__构造函数X=Class()__del__析构函数对象销毁__repr__打印转换print X，repr(X)__str__打印转换print X，str(X)__call__调用函数X()__getattr_限制X.undefine__setattr__取值X.any=value__getitem__索引X[key]，For If__setitem__索引X[key]=value__len__长度len(X)__iter__迭代

For In

__add__+X+Y,X+=Y__sub__-X-Y,X-=Y__mul__*X*Y__radd__右加++X__iadd__+=X+=Y__or__|X|Y,X|=Y__cmp__比较 ==X==Y,X<Y__lt__小于<X<Y__eq__等于=X=Y

减法重载

重载"-" 不同对象的减法处理

class Number:    def __init__(self,start):        self.data=start    def __sub__(self,other):         return Number(self.data-other)number=Number(20)y=number-10print number.data, y.data

重载"-" 相同对象的减法处理

class Big :     def __init__(self,a,b):         self.a=a         self.b=b     def __sub__(self,other):#other不用事先制定类型,可以直接当做一个Big来用        return Big(self.a-other.a,self.b-other.b)i=Big(20,12);j=Big(23,4);k=i-j;print k.a ,k.b

重载"+"

class AddOperator :     def __init__(self,a,b):         self.a=a         self.b=b     def __add__(self,other):#other不用事先制定类型,可以直接当做一个Big来用        return Big(self.a+other.a,self.b+other.b)i=AddOperator(20,12);j=AddOperator(23,4);k=i+j;print k.a ,k.b

重载"+="

class AddOperator :     def __init__(self,a,b):         self.a=a         self.b=b     def __iadd__(self,other):#other不用事先制定类型,可以直接当做一个Big来用        return Big(self.a+other.a,self.b+other.b)i=AddOperator(20,12);j=AddOperator(23,4);i+=j;print i.a ,i.b

重载乘法

不同对象的乘法：

class MulOperator:    def __init__(self,a,b):        self.a=a        self.b=b    def __mul__(self,n):        return MulOperator(self.a*n,self.b*n)i=MulOperator(20,5)j=i*4.5print j.a,j.b

重载乘法：两个对象的相乘似乎也有用，如矩阵的相乘，3D中几个变换矩阵的相乘。
两个4*4矩阵相乘
矩阵 的列数必须等于矩阵 的行数，矩阵 与矩阵 才能相乘，第一个矩阵由4个横向排列的四维向量组成，第二个矩阵由4个纵向排列的四维向量组成，

class Vector4:     def __init__(self,a,b,c,d):       (self.a1,self.a2,self.a3,self.a4)=(a,b,c,d)    def __mul__(self,other):         return (self.a1*other.a1+self.a2*other.a2+self.a3*other.a3+self.a4*other.a4)    def PrintVector(self):        print self.a1,self.a2,self.a3,self.a4class Matrix :    def __init__(self,a,b,c,d):        (self.a1,self.a2,self.a3,self.a4)=(a,b,c,d)        #(self.a1,self.a2,self.a3,self.a4)=(a,b,c,d)    def __mul__(self,other):        x1=Vector4(other.a1.a1,other.a2.a1,other.a3.a1,other.a4.a1)        x2=Vector4(other.a1.a2,other.a2.a2,other.a3.a2,other.a4.a2)        x3=Vector4(other.a1.a3,other.a2.a3,other.a3.a3,other.a4.a3)        x4=Vector4(other.a1.a4,other.a2.a4,other.a3.a4,other.a4.a4)        a=Vector4(self.a1*x1,self.a1*x2,self.a1*x3,self.a1*x4)        b=Vector4(self.a2*x1,self.a2*x2,self.a2*x3,self.a2*x4)        c=Vector4(self.a3*x1,self.a3*x2,self.a3*x3,self.a3*x4)        d=Vector4(self.a4*x1,self.a4*x2,self.a4*x3,self.a4*x4)        return Matrix(a,b,c,d)    def PrintMatrix(self):         self.a1.PrintVector()         self.a2.PrintVector()         self.a3.PrintVector()         self.a4.PrintVector()i1=Vector4(1,4,1,4)i2=Vector4(2,1,6,7)k=i1*i2#测试向量点乘print ki3=Vector4(1,1,1,1)i4=Vector4(1,2,4,5)j1=Vector4(1,2,3,4)j2=Vector4(2,1,1,1)j3=Vector4(1,3,21,2)j4=Vector4(2,4,3,7)a=Matrix(i1,i2,i3,i4)b=Matrix(j1,j2,j3,j4)c=a*bc.PrintMatrix()

索引重载

class indexer:        def __getitem__(self, index): #iter override            return index ** 2  X = indexer()    X[2]    for i in range(5):        print X[i]        class indexer:        def __setitem__(self, key,value): #iter override              self.mydict[key] = value         return self.mydict X = indexer()   X[2] = 'test'  它等于调用 X.__setitem__(2, 'test') 

打印重载

class adder :    def __init__(self,value=0):           self.data=value    def __add__(self,other):           self.data+=otherclass addrepr(adder):    def __repr__(self):          return "addrepr(%d)"% self.data #%d ,%s都可以 x=addrepr(2)x+1print x ,repr(x)i=3;print "%s---%d"% (i, i)

调用重载，__call__相当与 X()

class Prod:        def __init__(self, value):            self.value = value        def __call__(self, other):            return self.value * other       p = Prod(2) #call __init__    print p(1) #call __call__    print p(2)

析构重载 __del__

class Life:        def __init__(self, name='name'):            print 'Hello', name            self.name = name        def __del__(self):            print 'Goodby', self.name       brain = Life('Brain') #call __init__    brain = 'loretta'    # call __del__

重载"|"

class Mat :    def __init__(self,value):       self.age=value    def __or__(self,other):        return self.age!=0 and other.age!=0a=Mat(10)b=Mat(21)c=Mat(0)print a|b ,a|c

打印转换重载

class PrintOperator:    def __init__(self,a):        self.a=a    def __str__(self,b=50):       return "I am %s years old!" % self.ai=PrintOperator(10)print i, str(i)

长度重载

class lenOperator:    def __init__(self,a,b,c):         (self.a,self.b,self.c)=(a,b,c)    def __len__(self):        return 3a=lenOperator(0,2,4)print len(a)

cmp重载

class cmpOperator:    def __init__(self,a,b,c):        (self.a,self.b,self.c)=(a,b,c)    def __cmp__(self,other):        if self.a>other.a:           return 1        elif self.a<other.a:           return -1        elif self.b>other.b:           return 1        elif self.b<other.b:            return -1        elif self.c>self.c:            return 1        elif self.c<self.c:            return -1        elif self.c==self.c:           return 0    i=cmpOperator(1,2,3)j=cmpOperator(2,4,5)k=cmpOperator(2,4,5)a=cmpOperator(1,4,5)print cmp(i,j),cmp(j,k),cmp(a,i)

delattr重载

class delattrOperator(object):     def __init__(self,a,b):        (self.a,self.b)=(a,b)     def __delattr__(self,name):        print "del obj.%s" % name        object.__delattr__(self,name)a=delattrOperator(1,2)print a.a,a.bdel a.aprint a.b#print a.a 打印a会出错，a已经被删除。

getAttr/setAttr重载

class empty:        def __getattr__(self,attrname):            if attrname == 'age':                return 40           else:                raise AttributeError,attrname    X = empty()    print X.age #call__getattr__       class accesscontrol:        def __setattr__(self, attr, value):            if attr == 'age':                # Self.attrname = value loops!                self.__dict__[attr] = value            else:                print attr                raise AttributeError, attr + 'not allowed'      X = accesscontrol()    X.age = 40      #call __setattr__    X.name = 'wang' #raise exception