Here's my problem:
I have a class. And I have two objects of that class: ObjectOne and ObjectTwo
I'd like my class to have certain methods for ObjectOne and different methods for ObjectTwo.
I'd also like to choose those methods from a variety depending on some condition.
and of course, I need to call the methods I have 'from the outside code'
As I see the solution on my own (just logic, no code):
I make a default class. And I make a list of functions defined somewhere.
IF 'some condition' is True I construct a child class that takes one of those functions and adds it into class as class method. Otherwise I add some default set of methods. Then I make ObjectOne of this child class.
The question is: can I do that at all? And how do I do that? And how do I call such a method once it is added? They all would surely be named differently...
I do not ask for a piece of working code here. If you could give me a hint on where to look or maybe a certain topic to learn, this would do just fine!
PS: In case you wonder, the context is this: I am making a simple game prototype, and my objects represent two game units (characters) that fight each other automatically. Something like an auto-chess. Each unit may have unique abilities and therefore should act (make decisions on the battlefield) depending on the abilities it has. At first I tried to make a unified decision-making routine that would include all possible abilities at once (such as: if hasDoubleStrike else if... etc). But it turned out to be a very complex task, because there are tens of abilities overall, each unit may have any two, so the number of combinations is... vast. So, now I am trying to distribute this logic over separate units: each one would 'know' only of its own two abilities.
I mean I believe this is what would generally be referred to as a bad idea, but... you could have an argument passed into the class's constructor and then define the behavior/existence of a function depending on that condition. Like So:
class foo():
def __init__(self, condition):
if condition:
self.func = lambda : print('baz')
else:
self.func = lambda : print('bar')
if __name__ == '__main__':
obj1 = foo(True)
obj2 = foo(False)
obj1.func()
obj2.func()
Outputs:
baz
bar
You'd likely be better off just having different classes or setting up some sort of class hierarchy.
So in the end the best solution was the classical factory method and factory class. Like this:
import abc
import Actions # a module that works as a library of standard actions
def make_creature(some_params):
creature_factory = CreatureFactory()
tempCreature = creature_factory.make_creature(some_params)
return tempCreature
class CreatureFactory:
def make_creature(some_params):
...
if "foo" in some_params:
return fooChildCreature()
class ParentCreature(metaclass=abc.ABCMeta):
someStaticParams = 'abc'
#abc.abstractmethod
def decisionMaking():
pass
class fooChildCreature(ParentCreature):
def decisionMaking():
Actions.foo_action()
Actions.bar_action()
# some creature-specific decision making here that calls same static functions from 'Actions'
NewCreature = make_creature(some_params)
This is not ideal, this still requires much manual work to define decision making for various kinds of creatures, but it is still WAY better than anything else. Thank you very much for this advice.
Related
I have some functions that have implementation details that depend on which type of object is passed to them (specifically, it's to pick the proper method to link Django models to generate QuerySets). Which of the two following options is the more Pythonic way to implement things?
If ladders
def do_something(thing: SuperClass) -> "QuerySet[SomethingElse]":
if isinstance(thing, SubClassA):
return thing.property_set.all()
if isinstance(thing, SubClassB):
return thing.method()
if isinstance(thing, SubClassC):
return a_function(thing)
if isinstance(thing, SubClassD):
return SomethingElse.objects.filter(some_property__in=thing.another_property_set.all())
return SomethingElse.objects.none()
Dictionary
def do_something(thing: SuperClass) -> "QuerySet[SomethingElse]":
return {
SubClassA: thing.property_set.all(),
SubClassB: thing.method(),
SubClassC: a_function(thing),
SubClassD: SomethingElse.objects.filter(some_property__in=thing.another_property_set.all()),
}.get(type(thing), SomethingElse.objects.none())
The dictionary option has less repeated code and fewer lines but the if ladders make PyCharm & MyPy happier (especially with type-checking).
I assume that any performance difference between the two would be negligible unless it's in an inner loop of a frequently-called routine (as in >>1 request/second).
This is exactly the type of problem polymorphism aims to solve, and the "Pythonic" way to solve this problem is to use polymorphism. Following the notion to "encapsulate what varies", I'd recommend creating a base "interface" that all classes implement, then just call a method of the same name on all classes.
I put "interface" in quotation marks, because Python doesn't really have interfaces as they're commonly known in OOP. So, you'll have to make do with using subclasses, and enforcing the method signature manually (i.e. by being careful).
To demonstrate:
class SuperClass:
# define the method signature here (mostly for documentation purposes)
def do_something(self):
pass
class SubClassA(SuperClass):
# Be careful to override this method with the same signature as shown in
# SuperClass. (In this case, there aren't any arguments.)
def do_something(self):
print("Override A")
class SubClassB(SuperClass):
def do_something(self):
print("Override B")
if __name__ == '__main__':
import random
a = SubClassA()
b = SubClassB()
chosen = random.choice([a, b])
# We don't have to worry about which subclass was chosen, because they
# share the same interface. That is, we _know_ there will be a
# `do_something` method on it that takes no arguments.
chosen.do_something()
Python 3.6
I'm trying to modify the behavior of a third party library.
I don't want to directly change the source code.
Considering this code below:
class UselessObject(object):
pass
class PretendClassDef(object):
"""
A class to highlight my problem
"""
def do_something(self):
# Allot of code here
result = UselessObject()
return result
I'd like to substitute my own class for UselessObject
I'd like to know if using a metaclass in my module to intercept the creation of UselessObject is a valid idea?
EDIT
This answer posted by Ashwini Chaudhary on the same question, may be of use to others. As well as the below answer.
P.S. I also discovered that 'module' level __metaclass__ does't work in python 3. So my initial question of it 'being a valid idea' is False
FWIW, here's some code that illustrates Rawing's idea.
class UselessObject(object):
def __repr__(self):
return "I'm useless"
class PretendClassDef(object):
def do_something(self):
return UselessObject()
# -------
class CoolObject(object):
def __repr__(self):
return "I'm cool"
UselessObject = CoolObject
p = PretendClassDef()
print(p.do_something())
output
I'm cool
We can even use this technique if CoolObject needs to inherit UselessObject. If we change the definition of CoolObject to:
class CoolObject(UselessObject):
def __repr__(self):
s = super().__repr__()
return "I'm cool, but my parent says " + s
we get this output:
I'm cool, but my parent says I'm useless
This works because the name UselessObject has its old definition when the CoolObject class definition is executed.
This is not a job for metaclasses.
Rather, Python allows you to do this through a technique called "Monkeypatching", in which you, at run time, substitute one object for another in run time.
In this case, you'd be changing the thirdyparty.UselessObject for your.CoolObject before calling thirdyparty.PretendClassDef.do_something
The way to do that is a simple assignment.
So, supposing the example snippet you gave on the question is the trirdyparty module, on the library, your code would look like:
import thirdyparty
class CoolObject:
# Your class definition here
thirdyparty.UselesObject = Coolobject
Things you have to take care of: that you change the object pointed by UselessObject in the way it is used in your target module.
If for example, your PretendedClassDef and UselessObject are defined in different modules, you have to procees in one way if UselessObject is imported with from .useless import UselessObject (in this case the example above is fine), and import .useless and later uses it as useless.UselessObject - in this second case, you have to patch it on the useless module.
Also, Python's unittest.mock has a nice patch callable that can properly perform a monkeypatching and undo it if by some reason you want the modification to be valid in a limited scope, like inside a function of yours, or inside a with block. That might be the case if you don't want to change the behavior of the thirdyparty module in other sections of your program.
As for metaclasses, they only would be of any use if you would need to change the metaclass of a class you'd be replacing in this way - and them they only could have any use if you'd like to insert behavior in classes that inherit from UselessObject. In that case it would be used to create the local CoolObject and you'd still perform as above, but taking care that you'd perform the monkeypatching before Python would run the class body of any of the derived classes of UselessObject, taking extreme care when doing any imports from the thirdparty library (that would be tricky if these subclasses were defined on the same file)
This is just building on PM 2Ring's and jsbueno's answers with more contexts:
If you happen to be creating a library for others to use as a third-party library (rather than you using the third-party library), and if you need CoolObject to inherit UselessObject to avoid repetition, the following may be useful to avoid an infinite recursion error that you might get in some circumstances:
module1.py
class Parent:
def __init__(self):
print("I'm the parent.")
class Actor:
def __init__(self, parent_class=None):
if parent_class!=None: #This is in case you don't want it to actually literally be useless 100% of the time.
global Parent
Parent=parent_class
Parent()
module2.py
from module1 import *
class Child(Parent):
def __init__(self):
print("I'm the child.")
class LeadActor(Actor): #There's not necessarily a need to subclass Actor, but in the situation I'm thinking, it seems it would be a common thing.
def __init__(self):
Actor.__init__(self, parent_class=Child)
a=Actor(parent_class=Child) #prints "I'm the child." instead of "I'm the parent."
l=LeadActor() #prints "I'm the child." instead of "I'm the parent."
Just be careful that the user knows not to set a different value for parent_class with different subclasses of Actor. I mean, if you make multiple kinds of Actors, you'll only want to set parent_class once, unless you want it to change for all of them.
Using "new" style classes (I'm in python 3.2) is there a way to split a class over multiple files? I've got a large class (which really should be a single class from an object-oriented design perspective, considering coupling, etc, but it'd be nice to split over a few files just for ease of editing the class.
If your problem really is just working with a large class in an editor, the first solution I'd actually look for is a better way to break down the problem. The second solution would be a better editor, preferably one with code folding.
That said, there are a couple of ways you might break up a class into multiple files. Python lets you use a folder as a module by putting an __init__.py in it, which can then import things from other files. We'll use this capability in each solution. Make a folder called, say, bigclass first.
In the folder put the various .py files that will eventually comprise your class. Each should contain functions and variable definitions for the eventual class, not classes. In __init__.py in the same folder write the following to join them all together.
class Bigclass(object):
from classdef1 import foo, bar, baz, quux
from classdef2 import thing1, thing2
from classdef3 import magic, moremagic
# unfortunately, "from classdefn import *" is an error or warning
num = 42 # add more members here if you like
This has the advantage that you end up with a single class derived directly from object, which will look nice in your inheritance graphs.
You could use multiple inheritance to combine the various parts of your class. In your individual modules you would write a class definition for Bigclass with parts of the class. Then in your __init__.py write:
import classdef1, classdef2, classdef3
class Bigclass(classdef1.Bigclass, classdef2.Bigclass, classdef3.Bigclass):
num = 42 # add more members if desired
If the multiple inheritance becomes an issue, you can use single inheritance: just have each class inherit from another one in chain fashion. Assuming you don't define anything in more than one class, the order doesn't matter. For example, classdef2.py would be like:
import classdef1
class Bigclass(classdef1.Bigclass):
# more member defs here
classdef3 would import Bigclass from classdef2 and add to it, and so on. Your __init__.py would just import the last one:
from classdef42 import Bigclass
I'd generally prefer #1 because it's more explicit about what members you're importing from which files but any of these solutions could work for you.
To use the class in any of these scenarios you can just import it, using the folder name as the module name: from bigclass import Bigclass
You can do this with decorators like so:
class Car(object):
def start(self):
print 'Car has started'
def extends(klass):
def decorator(func):
setattr(klass, func.__name__, func)
return func
return decorator
#this can go in a different module/file
#extends(Car)
def do_start(self):
self.start()
#so can this
car = Car()
car.do_start()
#=> Car has started
Class definitions containing hundreds of lines do occur "in the wild" (I have seen some in popular open-source Python-based frameworks), but I believe that if you ponder what the methods are doing, it will be possible to reduce the length of most classes to a manageable point. Some examples:
Look for places where mostly the same code occurs more than once. Break that code out into its own method and call it from each place with arguments.
"Private" methods that do not use any of the object state can be brought out of the class as stand-alone functions.
Methods that should be called only under certain conditions may indicate a need to place those methods in a subclass.
To directly address your question, it is possible to split up the definition of a class. One way is to "monkey-patch" the class by defining it and then adding outside functions to it as methods. Another is to use the built-in type function to create the class "by hand", supplying its name, any base classes, and its methods and attributes in a dictionary. But I do not recommend doing this just because the definition would be long otherwise. That sort of cure is worse than the disease in my opinion.
I've previously toyed around with something similar. My usecase was a class hierarchy of nodes in an abstract syntax tree, and then I wanted to put all e.g. prettyprinting functions in a separate prettyprint.py file but still have them as methods in the classes.
One thing I tried was to use a decorator that puts the decorated function as an attribute on a specified class. In my case this would mean that prettyprint.py contains lots of def prettyprint(self) all decorated with different #inclass(...)
A problem with this is that one must make sure that the sub files are always imported, and that they depend on the main class, which makes for a circular dependency, which may be messy.
def inclass(kls):
"""
Decorator that adds the decorated function
as a method in specified class
"""
def _(func):
setattr(kls,func.__name__, func)
return func
return _
## exampe usage
class C:
def __init__(self, d):
self.d = d
# this would be in a separate file.
#inclass(C)
def meth(self, a):
"""Some method"""
print "attribute: %s - argument: %s" % (self.d, a)
i = C(10)
print i.meth.__doc__
i.meth(20)
I've not used it, but this package called partial claims to add support for partial classes.
It seems like there's a few other ways you could implement this yourself as well.
You could implement separate parts of the class as mixins in seperate files, then import them all somewhere and subclass them.
Alternatively, you could implement each of the methods of your class somewhere then in a central file import them and assign them as attributes on a class, to create the whole object. Like so:
a.py:
def AFunc( self, something ):
# Do something
pass
b.py:
def BFunc( self, something ):
# Do something else
pass
c.py:
import a, b
class C:
AFunc = a.AFunc
BFunc = b.BFunc
You could even go so far as to automate this process if you really wanted - loop through all the functions provided by modules a and b and then add them as attributes on C. Though that might be total overkill.
There might be other (possibly better) ways to go about it, but those are the 2 that popped into mind.
I would like to add that the pythonic way of doing this is through multiple inheritance, not necessarily using mixins. Instance attributes can be added using super().__init__(*args, **kwargs) in __init__ calls to pass arguments to baseclasses (see ‘super considered super’ presentation by Raymond Hettinger 1). This also enables dependency injection and kind of forces you to think about organization of base classes (it works best if only one baseclass sets an attribute in __init__ and all classes using the attribute inherit from it).
This does usually require you having control over the base classes (or they being written for this pattern).
Another option is using descriptors returning functions through __get__ to add functionality to classes in a decoupled way.
You could also look at __init_subclass__ to add e.g. methods to classes during class generation (i think added in python 3.6, but check)
First I'd like to say that something this complicated it probably not a good idea just to make finding your place in the class easier - it would be best to add comments, highlight sections etc. However, I see two ways you could do this:
Write the class in several files, then read them in as text, concatenate them and exec the resulting string.
Create a separate class in each file, then inherit them all into a master class as mixins. However, if you're subclassing another class already this could lead to MRO problems. You could get around this by creating a metaclass for your master class which manually resolves the MRO, but this could get messy.
The easiest would be the first option.
First off, I don't see how splitting the class into multiple files makes editing any easier. A decent IDE should be able to find any method easily whether in one file or multiple; if you're not using a decent IDE, splitting the class means the maintainer has to guess which file a given method is in, which sounds harder rather than easier.
More fundamentally, this class - so large that you want a special language feature just to support its weight - sounds fundamentally broken. How many lines of code are we talking about? Almost certainly, it would be a better idea to do one of:
Refactor duplicated code into fewer, more general primitives
Define a base class and extend it with subclasses as Karoly Horvath suggests in comments (this is the closest thing to the 'partial classes' that you're asking for that I would endorse)
Define a few separate classes to encapsulate different parts of this
class's functionality, and compose this class of instances of those
smaller ones.
I met the same situation - I want to slipt my class to 2 files.
the reason is that - I want part 1 for GUI layout, only layout
and another file keeps all function.
like c#'s Partial class. one for XAML and another one for functions.
Background
(Might be relevant because there might be a simpler way to achieve what I want.)
I want to build a declarative way to define "aspects" that can be analyzed by a static code analysis tool. The whole concept is written down here. Every aspect (say Redundancy) may have sub aspects recursively (say Redundancy.Clone) and every aspect shall have documentation and arbitrary other properties. The user shall be able to choose which aspects to analyze and I have to programmatically find out for the internal representation of an aspect if it's the one choosen by the user (i.e. for a given class Redundancy.Clone I want to validate that it belongs to a given string redundancy.clone but not redundancy.unused_import).
I decided to use classes like this:
class Redundancy(Aspect):
"""
This meta aspect describes any kind of redundancy in your source code.
"""
# Can't inherit from Redundancy here because of the recursion
class Clone(Aspect):
"""
This redundancy describes a code clone. Code clones are different pieces of
code in your codebase that are very similar.
"""
# Stuff...
Problem
For a given Aspect class I want to get the describing string (Redundancy.Clone -> redundancy.clone). For that I have to get the name of the surrounding module/class/whatever it is, check if it's a class (trivial) and construct a string out of it.
Possible Solutions and How They Failed
I did try looking at the dir of my classes to see if there's anything useful in the dunder methods I could use but found nothing except the repr which in the above case is <class 'coalib.bearlib.aspects.Redundancy.Clone'> when living in the aspects module. This shows that it should be possible but I have no idea on how repr gets this information and I would like to avoid using repr and stripping off the unneeded stuff as that's kind of a hack.
I am not able to inherit the nested class from the outer one as it is not completely defined yet. I want them nested for the usability, being able to from ... import Redundancy and in my source code write Redundancy.Clone is a huge plus.
Any suggestions, including changing my approach, would be appreciated.
You could use __qualname__ (PEP 3155)
>>> class C:
... def f(): pass
... class D:
... def g(): pass
...
>>> C.__qualname__
'C'
>>> C.f.__qualname__
'C.f'
>>> C.D.__qualname__
'C.D'
>>> C.D.g.__qualname__
'C.D.g'
You can construct the class after class Redundancy statement finish its execution with the type class. For example:
class Aspect:
pass
class Redundancy(Aspect):
#classmethod
def init(cls):
cls.make_Clone()
#classmethod
def make_Clone(cls):
def __init__(self):
print('inside Redundancy.Clone')
methods = {}
methods["__init__"] = __init__
cls.Clone = type("{0}.Clone".format(cls.__name__), (Redundancy,), methods )
Redundancy.init()
print(Redundancy.Clone)
print(Redundancy.Clone())
# output:
# <class '__main__.Redundancy.Clone'>
# inside Redundancy.Clone
# <__main__.Redundancy.Clone object at 0x01DCA130>
Using "new" style classes (I'm in python 3.2) is there a way to split a class over multiple files? I've got a large class (which really should be a single class from an object-oriented design perspective, considering coupling, etc, but it'd be nice to split over a few files just for ease of editing the class.
If your problem really is just working with a large class in an editor, the first solution I'd actually look for is a better way to break down the problem. The second solution would be a better editor, preferably one with code folding.
That said, there are a couple of ways you might break up a class into multiple files. Python lets you use a folder as a module by putting an __init__.py in it, which can then import things from other files. We'll use this capability in each solution. Make a folder called, say, bigclass first.
In the folder put the various .py files that will eventually comprise your class. Each should contain functions and variable definitions for the eventual class, not classes. In __init__.py in the same folder write the following to join them all together.
class Bigclass(object):
from classdef1 import foo, bar, baz, quux
from classdef2 import thing1, thing2
from classdef3 import magic, moremagic
# unfortunately, "from classdefn import *" is an error or warning
num = 42 # add more members here if you like
This has the advantage that you end up with a single class derived directly from object, which will look nice in your inheritance graphs.
You could use multiple inheritance to combine the various parts of your class. In your individual modules you would write a class definition for Bigclass with parts of the class. Then in your __init__.py write:
import classdef1, classdef2, classdef3
class Bigclass(classdef1.Bigclass, classdef2.Bigclass, classdef3.Bigclass):
num = 42 # add more members if desired
If the multiple inheritance becomes an issue, you can use single inheritance: just have each class inherit from another one in chain fashion. Assuming you don't define anything in more than one class, the order doesn't matter. For example, classdef2.py would be like:
import classdef1
class Bigclass(classdef1.Bigclass):
# more member defs here
classdef3 would import Bigclass from classdef2 and add to it, and so on. Your __init__.py would just import the last one:
from classdef42 import Bigclass
I'd generally prefer #1 because it's more explicit about what members you're importing from which files but any of these solutions could work for you.
To use the class in any of these scenarios you can just import it, using the folder name as the module name: from bigclass import Bigclass
You can do this with decorators like so:
class Car(object):
def start(self):
print 'Car has started'
def extends(klass):
def decorator(func):
setattr(klass, func.__name__, func)
return func
return decorator
#this can go in a different module/file
#extends(Car)
def do_start(self):
self.start()
#so can this
car = Car()
car.do_start()
#=> Car has started
Class definitions containing hundreds of lines do occur "in the wild" (I have seen some in popular open-source Python-based frameworks), but I believe that if you ponder what the methods are doing, it will be possible to reduce the length of most classes to a manageable point. Some examples:
Look for places where mostly the same code occurs more than once. Break that code out into its own method and call it from each place with arguments.
"Private" methods that do not use any of the object state can be brought out of the class as stand-alone functions.
Methods that should be called only under certain conditions may indicate a need to place those methods in a subclass.
To directly address your question, it is possible to split up the definition of a class. One way is to "monkey-patch" the class by defining it and then adding outside functions to it as methods. Another is to use the built-in type function to create the class "by hand", supplying its name, any base classes, and its methods and attributes in a dictionary. But I do not recommend doing this just because the definition would be long otherwise. That sort of cure is worse than the disease in my opinion.
I've previously toyed around with something similar. My usecase was a class hierarchy of nodes in an abstract syntax tree, and then I wanted to put all e.g. prettyprinting functions in a separate prettyprint.py file but still have them as methods in the classes.
One thing I tried was to use a decorator that puts the decorated function as an attribute on a specified class. In my case this would mean that prettyprint.py contains lots of def prettyprint(self) all decorated with different #inclass(...)
A problem with this is that one must make sure that the sub files are always imported, and that they depend on the main class, which makes for a circular dependency, which may be messy.
def inclass(kls):
"""
Decorator that adds the decorated function
as a method in specified class
"""
def _(func):
setattr(kls,func.__name__, func)
return func
return _
## exampe usage
class C:
def __init__(self, d):
self.d = d
# this would be in a separate file.
#inclass(C)
def meth(self, a):
"""Some method"""
print "attribute: %s - argument: %s" % (self.d, a)
i = C(10)
print i.meth.__doc__
i.meth(20)
I've not used it, but this package called partial claims to add support for partial classes.
It seems like there's a few other ways you could implement this yourself as well.
You could implement separate parts of the class as mixins in seperate files, then import them all somewhere and subclass them.
Alternatively, you could implement each of the methods of your class somewhere then in a central file import them and assign them as attributes on a class, to create the whole object. Like so:
a.py:
def AFunc( self, something ):
# Do something
pass
b.py:
def BFunc( self, something ):
# Do something else
pass
c.py:
import a, b
class C:
AFunc = a.AFunc
BFunc = b.BFunc
You could even go so far as to automate this process if you really wanted - loop through all the functions provided by modules a and b and then add them as attributes on C. Though that might be total overkill.
There might be other (possibly better) ways to go about it, but those are the 2 that popped into mind.
I would like to add that the pythonic way of doing this is through multiple inheritance, not necessarily using mixins. Instance attributes can be added using super().__init__(*args, **kwargs) in __init__ calls to pass arguments to baseclasses (see ‘super considered super’ presentation by Raymond Hettinger 1). This also enables dependency injection and kind of forces you to think about organization of base classes (it works best if only one baseclass sets an attribute in __init__ and all classes using the attribute inherit from it).
This does usually require you having control over the base classes (or they being written for this pattern).
Another option is using descriptors returning functions through __get__ to add functionality to classes in a decoupled way.
You could also look at __init_subclass__ to add e.g. methods to classes during class generation (i think added in python 3.6, but check)
First I'd like to say that something this complicated it probably not a good idea just to make finding your place in the class easier - it would be best to add comments, highlight sections etc. However, I see two ways you could do this:
Write the class in several files, then read them in as text, concatenate them and exec the resulting string.
Create a separate class in each file, then inherit them all into a master class as mixins. However, if you're subclassing another class already this could lead to MRO problems. You could get around this by creating a metaclass for your master class which manually resolves the MRO, but this could get messy.
The easiest would be the first option.
First off, I don't see how splitting the class into multiple files makes editing any easier. A decent IDE should be able to find any method easily whether in one file or multiple; if you're not using a decent IDE, splitting the class means the maintainer has to guess which file a given method is in, which sounds harder rather than easier.
More fundamentally, this class - so large that you want a special language feature just to support its weight - sounds fundamentally broken. How many lines of code are we talking about? Almost certainly, it would be a better idea to do one of:
Refactor duplicated code into fewer, more general primitives
Define a base class and extend it with subclasses as Karoly Horvath suggests in comments (this is the closest thing to the 'partial classes' that you're asking for that I would endorse)
Define a few separate classes to encapsulate different parts of this
class's functionality, and compose this class of instances of those
smaller ones.
I met the same situation - I want to slipt my class to 2 files.
the reason is that - I want part 1 for GUI layout, only layout
and another file keeps all function.
like c#'s Partial class. one for XAML and another one for functions.