7-8 如何通过实例方法名字的字符串调用方法

Posted 2020-11-03 石中玉smulngy

三个接口：

方法一：

>>> help(getattr)
Help on built-in function getattr in module __builtin__:

getattr(...)
    getattr(object, name[, default]) -> value
    
    Get a named attribute from an object; getattr(x, \'y\') is equivalent to x.y.
    When a default argument is given, it is returned when the attribute doesn\'t
    exist; without it, an exception is raised in that case.

help(getattr)

输出结果：

方法二：

 

>>> from operator import methodcaller

>>> help(methodcaller)
Help on class methodcaller in module operator:

class methodcaller(__builtin__.object)
 |  methodcaller(name, ...) --> methodcaller object
 |  
 |  Return a callable object that calls the given method on its operand.
 |  After f = methodcaller(\'name\'), the call f(r) returns r.name().
 |  After g = methodcaller(\'name\', \'date\', foo=1), the call g(r) returns
 |  r.name(\'date\', foo=1).
 |  
 |  Methods defined here:
 |  
 |  __call__(...)
 |      x.__call__(...) <==> x(...)
 |  
 |  __getattribute__(...)
 |      x.__getattribute__(\'name\') <==> x.name
 |  
 |  ----------------------------------------------------------------------
 |  Data and other attributes defined here:
 |  
 |  __new__ = <built-in method __new__ of type object>
 |      T.__new__(S, ...) -> a new object with type S, a subtype of T

help(methodcaller)

例子：

>>> s = \'abc123abc456\'
>>> s.find(\'abc\',4)
6

>>> strfindabc4 = methodcaller(\'find\',\'abc\',4)  #methodcaller创建一个对象，methodcaller（）第一个参数是要调用的函数方法的名字（字符串），其他参数是那个函数方法的参数。
>>> strfindabc4
<operator.methodcaller object at 0x0285ABC0>
>>> strfindabc4(s)      #再将原对象  作为参数传入
6