我已经了解到,可以在Python中向现有对象(即,不在类定义中)添加方法。
我明白这样做并不总是好的。但你怎么能做到这一点呢?
我已经了解到,可以在Python中向现有对象(即,不在类定义中)添加方法。
我明白这样做并不总是好的。但你怎么能做到这一点呢?
当前回答
我相信你要找的是setattr。使用此设置对象的属性。
>>> def printme(s): print repr(s)
>>> class A: pass
>>> setattr(A,'printme',printme)
>>> a = A()
>>> a.printme() # s becomes the implicit 'self' variable
< __ main __ . A instance at 0xABCDEFG>
其他回答
至少有两种方法可以将方法附加到没有类型的实例。MethodType:
>>> class A:
... def m(self):
... print 'im m, invoked with: ', self
>>> a = A()
>>> a.m()
im m, invoked with: <__main__.A instance at 0x973ec6c>
>>> a.m
<bound method A.m of <__main__.A instance at 0x973ec6c>>
>>>
>>> def foo(firstargument):
... print 'im foo, invoked with: ', firstargument
>>> foo
<function foo at 0x978548c>
1:
>>> a.foo = foo.__get__(a, A) # or foo.__get__(a, type(a))
>>> a.foo()
im foo, invoked with: <__main__.A instance at 0x973ec6c>
>>> a.foo
<bound method A.foo of <__main__.A instance at 0x973ec6c>>
2:
>>> instancemethod = type(A.m)
>>> instancemethod
<type 'instancemethod'>
>>> a.foo2 = instancemethod(foo, a, type(a))
>>> a.foo2()
im foo, invoked with: <__main__.A instance at 0x973ec6c>
>>> a.foo2
<bound method instance.foo of <__main__.A instance at 0x973ec6c>>
有用的链接:数据模型-调用描述符描述符操作指南-调用描述符
感谢Arturo!你的回答让我步入正轨!
根据Arturo的代码,我编写了一个小类:
from types import MethodType
import re
from string import ascii_letters
class DynamicAttr:
def __init__(self):
self.dict_all_files = {}
def _copy_files(self, *args, **kwargs):
print(f'copy {args[0]["filename"]} {args[0]["copy_command"]}')
def _delete_files(self, *args, **kwargs):
print(f'delete {args[0]["filename"]} {args[0]["delete_command"]}')
def _create_properties(self):
for key, item in self.dict_all_files.items():
setattr(
self,
key,
self.dict_all_files[key],
)
setattr(
self,
key + "_delete",
MethodType(
self._delete_files,
{
"filename": key,
"delete_command": f'del {item}',
},
),
)
setattr(
self,
key + "_copy",
MethodType(
self._copy_files,
{
"filename": key,
"copy_command": f'copy {item}',
},
),
)
def add_files_to_class(self, filelist: list):
for _ in filelist:
attr_key = re.sub(rf'[^{ascii_letters}]+', '_', _).strip('_')
self.dict_all_files[attr_key] = _
self._create_properties()
dy = DynamicAttr()
dy.add_files_to_class([r"C:\Windows\notepad.exe", r"C:\Windows\regedit.exe"])
dy.add_files_to_class([r"C:\Windows\HelpPane.exe", r"C:\Windows\win.ini"])
#output
print(dy.C_Windows_HelpPane_exe)
dy.C_Windows_notepad_exe_delete()
dy.C_Windows_HelpPane_exe_copy()
C:\Windows\HelpPane.exe
delete C_Windows_notepad_exe del C:\Windows\notepad.exe
copy C_Windows_HelpPane_exe copy C:\Windows\HelpPane.exe
此类允许您随时添加新的属性和方法。
编辑:
这里有一个更普遍的解决方案:
import inspect
import re
from copy import deepcopy
from string import ascii_letters
def copy_func(f):
if callable(f):
if inspect.ismethod(f) or inspect.isfunction(f):
g = lambda *args, **kwargs: f(*args, **kwargs)
t = list(filter(lambda prop: not ("__" in prop), dir(f)))
i = 0
while i < len(t):
setattr(g, t[i], getattr(f, t[i]))
i += 1
return g
dcoi = deepcopy([f])
return dcoi[0]
class FlexiblePartial:
def __init__(self, func, this_args_first, *args, **kwargs):
try:
self.f = copy_func(func) # create a copy of the function
except Exception:
self.f = func
self.this_args_first = this_args_first # where should the other (optional) arguments be that are passed when the function is called
try:
self.modulename = args[0].__class__.__name__ # to make repr look good
except Exception:
self.modulename = "self"
try:
self.functionname = func.__name__ # to make repr look good
except Exception:
try:
self.functionname = func.__qualname__ # to make repr look good
except Exception:
self.functionname = "func"
self.args = args
self.kwargs = kwargs
self.name_to_print = self._create_name() # to make repr look good
def _create_name(self):
stra = self.modulename + "." + self.functionname + "(self, "
for _ in self.args[1:]:
stra = stra + repr(_) + ", "
for key, item in self.kwargs.items():
stra = stra + str(key) + "=" + repr(item) + ", "
stra = stra.rstrip().rstrip(",")
stra += ")"
if len(stra) > 100:
stra = stra[:95] + "...)"
return stra
def __call__(self, *args, **kwargs):
newdic = {}
newdic.update(self.kwargs)
newdic.update(kwargs)
if self.this_args_first:
return self.f(*self.args[1:], *args, **newdic)
else:
return self.f(*args, *self.args[1:], **newdic)
def __str__(self):
return self.name_to_print
def __repr__(self):
return self.__str__()
class AddMethodsAndProperties:
def add_methods(self, dict_to_add):
for key_, item in dict_to_add.items():
key = re.sub(rf"[^{ascii_letters}]+", "_", str(key_)).rstrip("_")
if isinstance(item, dict):
if "function" in item: # for adding methods
if not isinstance(
item["function"], str
): # for external functions that are not part of the class
setattr(
self,
key,
FlexiblePartial(
item["function"],
item["this_args_first"],
self,
*item["args"],
**item["kwargs"],
),
)
else:
setattr(
self,
key,
FlexiblePartial(
getattr(
self, item["function"]
), # for internal functions - part of the class
item["this_args_first"],
self,
*item["args"],
**item["kwargs"],
),
)
else: # for adding props
setattr(self, key, item)
让我们测试一下:
class NewClass(AddMethodsAndProperties): #inherit from AddMethodsAndProperties to add the method add_methods
def __init__(self):
self.bubu = 5
def _delete_files(self, file): #some random methods
print(f"File will be deleted: {file}")
def delete_files(self, file):
self._delete_files(file)
def _copy_files(self, file, dst):
print(f"File will be copied: {file} Dest: {dst}")
def copy_files(self, file, dst):
self._copy_files(file, dst)
def _create_files(self, file, folder):
print(f"File will be created: {file} {folder}")
def create_files(self, file, folder):
self._create_files(file, folder)
def method_with_more_kwargs(self, file, folder, one_more):
print(file, folder, one_more)
return self
nc = NewClass()
dict_all_files = {
r"C:\Windows\notepad.exe_delete": {
"function": "delete_files",
"args": (),
"kwargs": {"file": r"C:\Windows\notepad.exe"},
"this_args_first": True,
},
r"C:\Windows\notepad.exe_argsfirst": {
"function": "delete_files",
"args": (),
"kwargs": {"file": r"C:\Windows\notepad.exe"},
"this_args_first": True,
},
r"C:\Windows\notepad.exe_copy": {
"function": "copy_files",
"args": (),
"kwargs": {
"file": r"C:\Windows\notepad.exe",
"dst": r"C:\Windows\notepad555.exe",
},
"this_args_first": True,
},
r"C:\Windows\notepad.exe_create": {
"function": "create_files",
"args": (),
"kwargs": {"file": r"C:\Windows\notepad.exe", "folder": "c:\\windows95"},
"this_args_first": True,
},
r"C:\Windows\notepad.exe_upper": {
"function": str.upper,
"args": (r"C:\Windows\notepad.exe",),
"kwargs": {},
"this_args_first": True,
},
r"C:\Windows\notepad.exe_method_with_more_kwargs": {
"function": "method_with_more_kwargs",
"args": (),
"kwargs": {"file": r"C:\Windows\notepad.exe", "folder": "c:\\windows95"},
"this_args_first": True,
},
r"C:\Windows\notepad.exe_method_with_more_kwargs_as_args_first": {
"function": "method_with_more_kwargs",
"args": (r"C:\Windows\notepad.exe", "c:\\windows95"),
"kwargs": {},
"this_args_first": True,
},
r"C:\Windows\notepad.exe_method_with_more_kwargs_as_args_last": {
"function": "method_with_more_kwargs",
"args": (r"C:\Windows\notepad.exe", "c:\\windows95"),
"kwargs": {},
"this_args_first": False,
},
"this_is_a_list": [55, 3, 3, 1, 4, 43],
}
nc.add_methods(dict_all_files)
print(nc.C_Windows_notepad_exe_delete)
print(nc.C_Windows_notepad_exe_delete(), end="\n\n")
print(nc.C_Windows_notepad_exe_argsfirst)
print(nc.C_Windows_notepad_exe_argsfirst(), end="\n\n")
print(nc.C_Windows_notepad_exe_copy)
print(nc.C_Windows_notepad_exe_copy(), end="\n\n")
print(nc.C_Windows_notepad_exe_create)
print(nc.C_Windows_notepad_exe_create(), end="\n\n")
print(nc.C_Windows_notepad_exe_upper)
print(nc.C_Windows_notepad_exe_upper(), end="\n\n")
print(nc.C_Windows_notepad_exe_method_with_more_kwargs)
print(
nc.C_Windows_notepad_exe_method_with_more_kwargs(
one_more="f:\\blaaaaaaaaaaaaaaaaaaaaaaaa"
)
.C_Windows_notepad_exe_method_with_more_kwargs(
one_more="f:\\ASJVASDFASÇDFJASÇDJFÇASWFJASÇ"
)
.C_Windows_notepad_exe_method_with_more_kwargs(
one_more="f:\\XXXXXXXXXXXXXXXXXXXXXXXXXXXXXX"
),
end="\n\n",
)
print(nc.C_Windows_notepad_exe_method_with_more_kwargs_as_args_first)
print(
nc.C_Windows_notepad_exe_method_with_more_kwargs_as_args_first(
"f:\\blaaaaaaaaaaaaaaaaaaaaaaaa"
),
end="\n\n",
)
print(
nc.C_Windows_notepad_exe_method_with_more_kwargs_as_args_first(
"f:\\blaaaaaaaaaaaaaaaaaaaaaaaa"
)
.C_Windows_notepad_exe_method_with_more_kwargs_as_args_first(
"f:\\ASJVASDFASÇDFJASÇDJFÇASWFJASÇ"
)
.C_Windows_notepad_exe_method_with_more_kwargs_as_args_first(
"f:\\XXXXXXXXXXXXXXXXXXXXXXXXXXXXXX"
),
end="\n\n",
)
print(nc.C_Windows_notepad_exe_method_with_more_kwargs_as_args_last)
print(
nc.C_Windows_notepad_exe_method_with_more_kwargs_as_args_last(
"f:\\blaaaaaaaaaaaaaaaaaaaaaaaa"
)
.C_Windows_notepad_exe_method_with_more_kwargs_as_args_last(
"f:\\ASJVASDFASÇDFJASÇDJFÇASWFJASÇ"
)
.C_Windows_notepad_exe_method_with_more_kwargs_as_args_last(
"f:\\XXXXXXXXXXXXXXXXXXXXXXXXXXXXXX"
),
end="\n\n",
)
print(
nc.C_Windows_notepad_exe_method_with_more_kwargs_as_args_last(
"f:\\blaaaaaaaaaaaaaaaaaaaaaaaa"
)
.C_Windows_notepad_exe_method_with_more_kwargs_as_args_last(
"f:\\ASJVASDFASÇDFJASÇDJFÇASWFJASÇ"
)
.C_Windows_notepad_exe_method_with_more_kwargs_as_args_last(
"f:\\XXXXXXXXXXXXXXXXXXXXXXXXXXXXXX"
),
end="\n\n",
)
print(nc.this_is_a_list)
checkit = (
nc.C_Windows_notepad_exe_method_with_more_kwargs_as_args_last(
"f:\\blaaaaaaaaaaaaaaaaaaaaaaaa"
)
.C_Windows_notepad_exe_method_with_more_kwargs_as_args_last(
"f:\\ASJVASDFASÇDFJASÇDJFÇASWFJASÇ"
)
.C_Windows_notepad_exe_method_with_more_kwargs_as_args_last(
"f:\\XXXXXXXXXXXXXXXXXXXXXXXXXXXXXX"
)
)
print(f'nc is checkit? -> {nc is checkit}')
#output:
NewClass.delete_files(self, file='C:\\Windows\\notepad.exe')
File will be deleted: C:\Windows\notepad.exe
None
NewClass.delete_files(self, file='C:\\Windows\\notepad.exe')
File will be deleted: C:\Windows\notepad.exe
None
NewClass.copy_files(self, file='C:\\Windows\\notepad.exe', dst='C:\\Windows\\notepad555.exe')
File will be copied: C:\Windows\notepad.exe Dest: C:\Windows\notepad555.exe
None
NewClass.create_files(self, file='C:\\Windows\\notepad.exe', folder='c:\\windows95')
File will be created: C:\Windows\notepad.exe c:\windows95
None
NewClass.upper(self, 'C:\\Windows\\notepad.exe')
C:\WINDOWS\NOTEPAD.EXE
NewClass.method_with_more_kwargs(self, file='C:\\Windows\\notepad.exe', folder='c:\\windows95')
C:\Windows\notepad.exe c:\windows95 f:\blaaaaaaaaaaaaaaaaaaaaaaaa
C:\Windows\notepad.exe c:\windows95 f:\ASJVASDFASÇDFJASÇDJFÇASWFJASÇ
C:\Windows\notepad.exe c:\windows95 f:\XXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
<__main__.NewClass object at 0x0000000005F199A0>
NewClass.method_with_more_kwargs(self, 'C:\\Windows\\notepad.exe', 'c:\\windows95')
C:\Windows\notepad.exe c:\windows95 f:\blaaaaaaaaaaaaaaaaaaaaaaaa
<__main__.NewClass object at 0x0000000005F199A0>
C:\Windows\notepad.exe c:\windows95 f:\blaaaaaaaaaaaaaaaaaaaaaaaa
C:\Windows\notepad.exe c:\windows95 f:\ASJVASDFASÇDFJASÇDJFÇASWFJASÇ
C:\Windows\notepad.exe c:\windows95 f:\XXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
<__main__.NewClass object at 0x0000000005F199A0>
NewClass.method_with_more_kwargs(self, 'C:\\Windows\\notepad.exe', 'c:\\windows95')
f:\blaaaaaaaaaaaaaaaaaaaaaaaa C:\Windows\notepad.exe c:\windows95
f:\ASJVASDFASÇDFJASÇDJFÇASWFJASÇ C:\Windows\notepad.exe c:\windows95
f:\XXXXXXXXXXXXXXXXXXXXXXXXXXXXXX C:\Windows\notepad.exe c:\windows95
<__main__.NewClass object at 0x0000000005F199A0>
f:\blaaaaaaaaaaaaaaaaaaaaaaaa C:\Windows\notepad.exe c:\windows95
f:\ASJVASDFASÇDFJASÇDJFÇASWFJASÇ C:\Windows\notepad.exe c:\windows95
f:\XXXXXXXXXXXXXXXXXXXXXXXXXXXXXX C:\Windows\notepad.exe c:\windows95
<__main__.NewClass object at 0x0000000005F199A0>
[55, 3, 3, 1, 4, 43]
f:\blaaaaaaaaaaaaaaaaaaaaaaaa C:\Windows\notepad.exe c:\windows95
f:\ASJVASDFASÇDFJASÇDJFÇASWFJASÇ C:\Windows\notepad.exe c:\windows95
f:\XXXXXXXXXXXXXXXXXXXXXXXXXXXXXX C:\Windows\notepad.exe c:\windows95
nc is checkit? -> True
杰森·普拉特发布的内容是正确的。
>>> class Test(object):
... def a(self):
... pass
...
>>> def b(self):
... pass
...
>>> Test.b = b
>>> type(b)
<type 'function'>
>>> type(Test.a)
<type 'instancemethod'>
>>> type(Test.b)
<type 'instancemethod'>
如您所见,Python认为b()与a()没有任何不同。在Python中,所有方法都只是恰好是函数的变量。
这实际上是对“杰森·普拉特”答案的补充
虽然Jasons的答案是有效的,但它只在想要向类中添加函数时有效。当我试图从.py源代码文件重新加载一个已经存在的方法时,它对我来说并不起作用。
我花了很长时间才找到解决方法,但技巧似乎很简单。。。1.从源代码文件导入代码2.强制重新加载3.rd使用types.FunctionType(…)将导入和绑定的方法转换为函数您还可以传递当前的全局变量,因为重新加载的方法将位于不同的命名空间中4.现在你可以按照“杰森·普拉特”的建议继续使用类型.MethodType(…)
例子:
# this class resides inside ReloadCodeDemo.py
class A:
def bar( self ):
print "bar1"
def reloadCode(self, methodName):
''' use this function to reload any function of class A'''
import types
import ReloadCodeDemo as ReloadMod # import the code as module
reload (ReloadMod) # force a reload of the module
myM = getattr(ReloadMod.A,methodName) #get reloaded Method
myTempFunc = types.FunctionType(# convert the method to a simple function
myM.im_func.func_code, #the methods code
globals(), # globals to use
argdefs=myM.im_func.func_defaults # default values for variables if any
)
myNewM = types.MethodType(myTempFunc,self,self.__class__) #convert the function to a method
setattr(self,methodName,myNewM) # add the method to the function
if __name__ == '__main__':
a = A()
a.bar()
# now change your code and save the file
a.reloadCode('bar') # reloads the file
a.bar() # now executes the reloaded code
如何从类的实例恢复类
class UnderWater:
def __init__(self):
self.net = 'underwater'
marine = UnderWater() # Instantiate the class
# Recover the class from the instance and add attributes to it.
class SubMarine(marine.__class__):
def __init__(self):
super().__init__()
self.sound = 'Sonar'
print(SubMarine, SubMarine.__name__, SubMarine().net, SubMarine().sound)
# Output
# (__main__.SubMarine,'SubMarine', 'underwater', 'Sonar')