python对象反射和函数反射

python的对象反射功能,经常在编程时使用.相比较其它的编程语言使用非常方便.反射就是用字符串来操作对象或者类,模块中的成员.

一.对象的反射

反射功能的实现,由这4个内置函数来实现(hasattr, getattr, setattr, delattr)

1.1.hasattr判断是否有某个成员

判断对象中是否有属性, 方法.返回bool值

#!/usr/bin/env python
# -*-coding:utf-8-*-

class Foo(object):
country = "china"

def __init__(self, name):
self.name = name

def f(self):
print "function f"

obj = Foo("abc")
print hasattr(obj, "name") #判断是否有name字段,返回True
print hasattr(obj, "f") #判断是否有f方法,返回True
print hasattr(obj, "ok") #没有这个方法,返回False
print hasattr(obj, "country") #判断有没有静态字段,返回True
print hasattr(Foo, "country") #使用类作为参数来判断
print "class:", Foo.__dict__.keys()
print "obj:", obj.__dict__.keys()

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#!/usr/bin/env python # -*-coding:utf-8-*-   class Foo(object):     country = "china"       def __init__(self, name):         self.name = name       def f(self):         print "function f"   obj = Foo("abc") print hasattr(obj, "name")         #判断是否有name字段,返回True print hasattr(obj, "f")            #判断是否有f方法,返回True print hasattr(obj, "ok")           #没有这个方法,返回False print hasattr(obj, "country")      #判断有没有静态字段,返回True print hasattr(Foo, "country")      #使用类作为参数来判断 print "class:", Foo.__dict__.keys() print "obj:", obj.__dict__.keys()

上例中使用对象作为obj参数来判断,是否有类的静态方法.也是可以的.因为对象的特殊性,先在对象中找是否有该成员,如果没在,通过对象指针,在去创建这个对象的类中找查

执行结果

True
True
False
True
True
class: ['__module__', 'f', 'country', '__dict__', '__weakref__', '__doc__', '__init__']
obj: ['name']

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True True False True True class: ['__module__', 'f', 'country', '__dict__', '__weakref__', '__doc__', '__init__'] obj: ['name']

1.2.获取对象的成员

也可以使用对象来获取类的成员.和上例中的hasattr一样

#!/usr/bin/env python
# -*-coding:utf-8-*-

class Foo(object):
country = "china"

def __init__(self, name):
self.name = name

def f(self):
print "this is function = ", self.name
obj = Foo("abc")
print getattr(obj, "name") #获取对象的name字段
f = getattr(obj, "f") #通过对象获取类的方法
print f #打印出来是信类的方法
f() #加上括号就能直接调用执行这个的方法
print getattr(Foo, "country")
print getattr(obj, "country") #使用对象也能找到静态字段

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#!/usr/bin/env python # -*-coding:utf-8-*-   class Foo(object):     country = "china"       def __init__(self, name):         self.name = name       def f(self):         print "this is function = ", self.name obj = Foo("abc") print getattr(obj, "name")             #获取对象的name字段 f = getattr(obj, "f")                  #通过对象获取类的方法 print f                                #打印出来是信类的方法 f()                                    #加上括号就能直接调用执行这个的方法 print getattr(Foo, "country") print getattr(obj, "country")          #使用对象也能找到静态字段

1.3.增加对象或者类的成员

动态的增加对象或者类中的成员

#!/usr/bin/env python
# -*-coding:utf-8-*-

class Foo(object):
country = "china"

def __init__(self, name):
self.name = name

def f(self):
print "this is function f.name = ", self.name

obj = Foo("abc")
setattr(obj, "age", 19) #增加普通字段
setattr(obj, "show", lambda num: num +1) #增加普通方法
setattr(Foo, "tel", "+086") #增加静态字段
print obj.age
print Foo.tel
print obj.show(10)

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#!/usr/bin/env python # -*-coding:utf-8-*-   class Foo(object):     country = "china"       def __init__(self, name):         self.name = name       def f(self):         print "this is function f.name = ", self.name     obj = Foo("abc") setattr(obj, "age", 19)                       #增加普通字段 setattr(obj, "show", lambda num: num +1)      #增加普通方法 setattr(Foo, "tel", "+086")                   #增加静态字段 print obj.age print Foo.tel print obj.show(10)

执行结果

19
+086
11

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19 +086 11

1.4.使用delattr动态的删除类或者方法成员

演示代码

#!/usr/bin/env python
# -*-coding:utf-8-*-

class Foo(object):
country = "china"

def __init__(self, name):
self.name = name

def f(self):
print "this is function f.name = ", self.name

obj = Foo("abc")
print getattr(obj, "name")
delattr(obj, "name") #删除掉了对象的普通字段name
print getattr(obj, "name")
print getattr(Foo, "country")
delattr(Foo, "country") #删除掉类的静态字段
print getattr(Foo, "country") #打印时说找不到些成员,报错

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#!/usr/bin/env python # -*-coding:utf-8-*-   class Foo(object):     country = "china"       def __init__(self, name):         self.name = name       def f(self):         print "this is function f.name = ", self.name     obj = Foo("abc") print getattr(obj, "name") delattr(obj, "name")                     #删除掉了对象的普通字段name print getattr(obj, "name") print getattr(Foo, "country") delattr(Foo, "country")                  #删除掉类的静态字段 print getattr(Foo, "country")            #打印时说找不到些成员,报错

执行结果

Traceback (most recent call last):
File "D:/����/python/��������/day08/blog/fanshe.py", line 17, in <module>
abc
print getattr(obj, "name")
AttributeError: 'Foo' object has no attribute 'name'

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Traceback (most recent call last): File "D:/����/python/��������/day08/blog/fanshe.py", line 17, in <module> abc print getattr(obj, "name") AttributeError: 'Foo' object has no attribute 'name'

二.在当前模块中使用反射

获取到对应的模块.

#!/usr/bin/env python
# -*-coding:utf-8-*-

import sys

data = "abc"
def f1():
print "f1 function"
def f2():
print "f2"

this_module = sys.modules[__name__]
print hasattr(this_module, "data") #使用反射
f1_get = getattr(this_module, "f1") #使用反射获取
f1_get()

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#!/usr/bin/env python # -*-coding:utf-8-*-   import sys   data = "abc" def f1():     print "f1 function" def f2():     print "f2"   this_module =  sys.modules[__name__] print hasattr(this_module, "data")             #使用反射 f1_get = getattr(this_module, "f1")            #使用反射获取 f1_get()

以上是反射对类,对象,模块成员操作的基本方法.

三.使用字符串自动导入模块

依据传入的字符串,自动导入模块.类似上文的方法反射

import importlib

my_moudle_name = "lib.aa"
aa = importlib.import_module(my_moudle_name)

print(aa)
print(aa.C().name)

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import importlib   my_moudle_name = "lib.aa" aa = importlib.import_module(my_moudle_name)   print(aa) print(aa.C().name)

执行结果

<module 'lib.aa' from 'D:\\python\\day10\\lib\\aa.py'>
ait24

1 2	<module 'lib.aa' from 'D:\\python\\day10\\lib\\aa.py'> ait24