Python中operator模块的操作符使用示例总结
operator模块是python中内置的操作符函数接口,它定义了一些算术和比较内置操作的函数。operator模块是用c实现的,所以执行速度比python代码快。 逻辑操作 from operator import * a = [1,2,3] b = a print 'a =',a print 'b =',b print print 'not_(a) :',not_(a) print 'truth(a) :',truth(a) print 'is_(a,b) :',is_(a,b) print 'is_not(a,b) :',is_not(a,b) 打印结果: a = [1,3] b = [1,3] not_(a) : False truth(a) : True is_(a,b) : True is_not(a,b): False 可以通过结果知道,operator的一些操作函数与原本的运算是相同的。 比较操作符 a = 3 b = 5 print 'a =',b print for func in (lt,le,eq,ne,ge,gt): print '{0}(a,b):'.format(func.__name__),func(a,b) 打印结果 a = 3 b = 5 lt(a,b): True le(a,b): True eq(a,b): False ne(a,b): True ge(a,b): False gt(a,b): False 这些函数等价于<、<=、==、>=和>的表达式语法。 算术操作符 a,b,c,d = -1,-3,4 print 'a =',b print 'c =',c print 'd =',d print 'nPositive/Negative:' print 'abs(a):',abs(a) print 'neg(a):',neg(a) print 'neg(b):',neg(b) print 'pos(a):',pos(a) print 'pos(b):',pos(b) 打印结果 a = -1 b = 2 c = -3 d = 4 Positive/Negative: abs(a): 1 neg(a): 1 neg(b): -2 pos(a): -1 pos(b): 2 abs返回值得绝对值,neg返回(-obj),pos返回(+obj)。 a = -2 b = 5.0 print 'a =',b print 'nArithmetic' print 'add(a,b) :',add(a,b) print 'div(a,div(a,b) print 'floordiv(a,floordiv(a,b) print 'mod(a,mod(a,b) print 'mul(a,mul(a,b) print 'pow(a,pow(a,b) print 'sub(a,sub(a,b) print 'truediv(a,truediv(a,b) 打印结果 a = -2 b = 5.0 Arithmetic add(a,b) : 3.0 div(a,b) : -0.4 floordiv(a,b) : -1.0 mod(a,b) : 3.0 # 查看负数取模 mul(a,b) : -10.0 pow(a,b) : -32.0 sub(a,b) : -7.0 truediv(a,b) : -0.4 mod表示取模, mul 表示相乘,pow是次方,sub表示相减 a = 2 b = 6 print 'a =',b print 'nBitwise:' print 'and_(a,and_(a,b) print 'invert(a) :',invert(a) print 'lshift(a,lshift(a,b) print 'or_(a,or_(a,b) print 'rshift(a,rshift(a,b) print 'xor(a,xor(a,b) 打印结果 a = 2 b = 6 Bitwise: and_(a,b) : 2 invert(a) : -3 lshift(a,b) : 128 or_(a,b) : 6 rshift(a,b) : 0 xor(a,b) : 4 and 表示按位与,invert 表示取反操作,lshift表示左位移,or表示按位或,rshift表示右位移,xor表示按位异或。
a = 3 b = 4 c = [1,2] d = ['a','b'] print 'a =',d print a = iadd(a,b) print 'a = iadd(a,b) =>',a print c = iconcat(c,d) print 'c = iconcat(c,d) =>',c 属性和元素的获取方法 from operator import * class MyObj(object): def __init__(self,arg): super(MyObj,self).__init__() self.arg = arg def __repr__(self): return 'MyObj(%s)' % self.arg objs = [MyObj(i) for i in xrange(5)] print "Object:",objs g = attrgetter("arg") vals = [g(i) for i in objs] print "arg values:",vals objs.reverse() print "reversed:",objs print "sorted:",sorted(objs,key=g) 结果: Object: [MyObj(0),MyObj(1),MyObj(2),MyObj(3),MyObj(4)] arg values: [0,1,3,4] reversed: [MyObj(4),MyObj(0)] sorted: [MyObj(0),MyObj(4)] 属性获取方法类似于 lambda x,n='attrname':getattr(x,nz) 元素获取方法类似于 lambda x,y=5:x[y] from operator import * l = [dict(val=-1*i) for i in xrange(4)] print "dictionaries:",l g = itemgetter("val") vals = [g(i) for i in l] print "values: ",vals print "sorted:",sorted(l,key=g) l = [(i,i*-2) for i in xrange(4)] print "tuples: ",l g = itemgetter(1) vals = [g(i) for i in l] print "values:",key=g) 结果如下: dictionaries: [{'val': 0},{'val': -1},{'val': -2},{'val': -3}] values: [0,-1,-2,-3] sorted: [{'val': -3},{'val': 0}] tuples: [(0,0),(1,-2),(2,-4),(3,-6)] values: [0,-4,-6] sorted: [(3,-6),(0,0)] 除了序列之外,元素获取方法还适用于映射。 结合操作符和定制类 from operator import * class MyObj(object): def __init__(self,val): super(MyObj,self).__init__() self.val = val return def __str__(self): return "MyObj(%s)" % self.val def __lt__(self,other): return self.val < other.val def __add__(self,other): return MyObj(self.val + other.val) a = MyObj(1) b = MyObj(2) print lt(a,b) print add(a,b) 结果如下所示: True MyObj(3) 类型检查 from operator import * class NoType(object): pass class MultiType(object): def __len__(self): return 0 def __getitem__(self,name): return "mapping" def __int__(self): return 0 o = NoType() t = MultiType() for func in [isMappingType,isNumberType,isSequenceType]: print "%s(o):" % func.__name__,func(o) print "%s(t):" % func.__name__,func(t) 结果如下: isMappingType(o): False isMappingType(t): True isNumberType(o): False isNumberType(t): True isSequenceType(o): False isSequenceType(t): True 但是这些测试并不完善,因为借口没有严格定义。 获取对象方法 from operator import methodcaller class Student(object): def __init__(self,name): self.name = name def getName(self): return self.name stu = Student("Jim") func = methodcaller('getName') print func(stu) # 输出Jim 还可以给方法传递参数: f=methodcaller('name','foo',bar=1) f(b) # return b.name('foo',bar=1) methodcaller方法等价于下面这个函数: def methodcaller(name,*args,**kwargs): def caller(obj): return getattr(obj,name)(*args,**kwargs) return caller (编辑:李大同) 【声明】本站内容均来自网络,其相关言论仅代表作者个人观点,不代表本站立场。若无意侵犯到您的权利,请及时与联系站长删除相关内容! |