Python内置函数(53)——repr

英文文档：

repr(object)

Return a string containing a printable representation of an object. For many types, this function makes an attempt to return a string that would yield an object with the same value when passed to eval(), otherwise the representation is a string enclosed in angle brackets that contains the name of the type of the object together with additional information often including the name and address of the object. A class can control what this function returns for its instances by defining a __repr__() method.

说明：

　　1. 函数功能返回一个对象的字符串表现形式。其功能和str函数比较类似，但是两者也有差异：函数str() 用于将值转化为适于人阅读的形式，而repr() 转化为供解释器读取的形式。

>>> a = 'some text'
>>> str(a)
'some text'
>>> repr(a)
"'some text'"

　　2. repr函数的结果一般能通过eval()求值的方法获取到原对象。

>>> eval(repr(a))
'some text'

　　3. 对于一般的类型，对其实例调用repr函数返回的是其所属的类型和被定义的模块，以及内存地址组成的字符串。

>>> class Student:
    def __init__(self,name):
        self.name = name

>>> a = Student('Bob')
>>> repr(a)
'<__main__.Student object at 0x037C4EB0>'

　　4. 如果要改变类型的repr函数显示信息，需要在类型中定义__repr__函数进行控制。

>>> class Student:
    def __init__(self,name):
        self.name = name
    def __repr__(self):
        return ('a student named ' + self.name)

>>> b = Student('Kim')
>>> repr(b)
'a student named Kim'