Python create empty object

Creating an empty object in Python

You can use type to create a new class on the fly and then instantiate it. Like so:

The arguments to type are: Class name, a tuple of base classes, and the object’s dictionary. Which can contain functions (the object’s methods) or attributes.

You can actually shorten the first line to

>>> t = type('test', (), <>)() >>> t.__class__.__bases__ (object,) 

Because by default type creates new style classes that inherit from object.

type is used in Python for metaprogramming.

But if you just want to create an instance of object. Then, just create an instance of it. Like lejlot suggests.

Creating an instance of a new class like this has an important difference that may be useful.

>>> a = object() >>> a.whoops = 1 Traceback (most recent call last): File "", line 1, in AttributeError: 'object' object has no attribute 'whoops' 

>>> b = type('', (), <>)() >>> b.this_works = 'cool' >>> 

aychedee 24041

Similar question

If there is a desired type of the empty object, in other words, you want to create it but don’t call the __init__ initializer, you can use __new__ :

class String(object): . uninitialized_empty_string = String.__new__(String) 

Constructs a new empty Set object. If the optional iterable parameter is supplied, updates the set with elements obtained from iteration. All of the elements in iterable should be immutable or be transformable to an immutable using the protocol described in section Protocol for automatic conversion to immutable.

myobj = set() for i in range(1,10): myobj.add(i) print(myobj) 

D z 105

Some more answer related to the same question

In my opinion, the easiest way is:

def x():pass x.test = 'Hello, world!' 

All the proposed solutions are somewhat awkward.

I found a way that is not hacky but is actually according to the original design.

>>> from mock import Mock >>> foo = Mock(spec=['foo'], foo='foo') >>> foo.foo 'foo' >>> foo.bar Traceback (most recent call last): File "", line 1, in File "/. /virtualenv/local/lib/python2.7/site-packages/mock/mock.py", line 698, in __getattr__ raise AttributeError("Mock object has no attribute %r" % name) AttributeError: Mock object has no attribute 'bar' 

Related question

x = lambda: [p for p in x.__dict__.keys()] 

x.p1 = 2 x.p2 = "Another property" 

[(p, getattr(x,p)) for p in x()] # gives # [('p1', 2), ('p2', 'Another property')] 

What do you mean by «empty object»? Instance of class object ? You can simply run

or maybe you mean initialization to the null reference? Then you can use

lejlot 62877

You said it in the question, but as no answer mentioned it with code, this is probably one of the cleanest solutions:

class Myobject: pass x = Myobject() x.test = "Hello, world!" # working 

One simple, less-terrifying-looking way to create an empty(-ish) object is to exploit the fact that functions are objects in Python, including Lambda Functions:

obj = lambda: None obj.test = "Hello, world!" 

In [18]: x = lambda: None In [19]: x.test = "Hello, world!" In [20]: x.test Out[20]: 'Hello, world!' 

Will 23114

Yes, in Python 3.3 SimpleNamespace was added

Unlike object, with SimpleNamespace you can add and remove attributes. If a SimpleNamespace object is initialized with keyword arguments, those are directly added to the underlying namespace.

import types x = types.SimpleNamespace() x.happy = True print(x.happy) # True del x.happy print(x.happy) # AttributeError. object has no attribute 'happy' 

Vlad Bezden 75920

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Источник

Creating an empty object in Python

You said it in the question, but as no answer mentioned it with code, this is probably one of the cleanest solutions:

class Myobject: pass x = Myobject() x.test = "Hello, world!" # working 

You can use type to create a new class on the fly and then instantiate it. Like so:

The arguments to type are: Class name, a tuple of base classes, and the object’s dictionary. Which can contain functions (the object’s methods) or attributes.

You can actually shorten the first line to

>>> t = type('test', (), <>)() >>> t.__class__.__bases__ (object,) 

Because by default type creates new style classes that inherit from object.

type is used in Python for metaprogramming.

But if you just want to create an instance of object. Then, just create an instance of it. Like lejlot suggests.

Creating an instance of a new class like this has an important difference that may be useful.

>>> a = object() >>> a.whoops = 1 Traceback (most recent call last): File "", line 1, in AttributeError: 'object' object has no attribute 'whoops' 

>>> b = type('', (), <>)() >>> b.this_works = 'cool' >>> 

Yes, in Python 3.3 SimpleNamespace was added

Unlike object, with SimpleNamespace you can add and remove attributes. If a SimpleNamespace object is initialized with keyword arguments, those are directly added to the underlying namespace.

import types x = types.SimpleNamespace() x.happy = True print(x.happy) # True del x.happy print(x.happy) # AttributeError. object has no attribute 'happy' 

One simple, less-terrifying-looking way to create an empty(-ish) object is to exploit the fact that functions are objects in Python, including Lambda Functions:

obj = lambda: None obj.test = "Hello, world!" 

In [18]: x = lambda: None In [19]: x.test = "Hello, world!" In [20]: x.test Out[20]: 'Hello, world!' 

Источник

How to create an empty class in Python?

A class in Python user-defined prototype for an object that defines a set of attributes that characterize any object of the class. The attributes are data members (class variables and instance variables) and methods, accessed via dot notation.

We can easily create an empty class in Python using the pass statement. This statement in Python do nothing. Let us see an example −

Create an empty class

Here, our class name is Amit −

Create an empty class with objects

Example

We can also create objects of an empty class and use it in our program −

class Amit: pass # Creating objects ob1 = Amit() ob2 = Amit() # Displaying print(ob1) print(ob2) 
 

Outpu

Create an empty class and set attributes for different objects

Example

In this example, we will create an empty class using the pass, but attributes will also be set for objects −

class Student: pass # Creating objects st1 = Student() st1.name = 'Henry' st1.age = 17 st1.marks = 90 st2 = Student() st2.name = 'Clark' st2.age = 16 st2.marks = 77 st2.phone = '120-6756-79' print('Student 1 = ', st1.name, st1.age, st1.marks) print('Student 2 = ', st2.name, st2.age, st2.marks, st2.phone) 
 

Output

Student 1 = Henry 17 90 Student 2 = Clark 16 77 120-6756-79

Using the pass statement, we can also create empty functions and loops. Let’s see −

Empty Function

Use the pass statement to write an empty function in Python −

# Empty function in Python def demo(): pass 

Above, we have created an empty function demo().

Empty if-else Statement

The pass statement can be used in an empty if-else statements −

a = True if (a == True) : pass else : print("False") 

Above, we have created an empty if-else statement.

Empty while Loop

The pass statement can also be used in an empty while loop −

cond = True while(cond == True): pass 

Источник