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Python Articles
Page 808 of 855
How to encode custom python objects as BSON with Pymongo?
To encode custom python objects as BSON with Pymongo, you have to write a SONManipulator. From the docs:SONManipulator instances allow you to specify transformations to be applied automatically by PyMongo.from pymongo.son_manipulator import SONManipulator class Transform(SONManipulator): def transform_incoming(self, son, collection): for (key, value) in son.items(): if isinstance(value, Custom): son[key] = encode_custom(value) elif isinstance(value, dict): # Make sure we recurse into sub-docs son[key] = self.transform_incoming(value, collection) return son def transform_outgoing(self, son, collection): for (key, value) in son.items(): ...
Read MoreHow I can create Python class from JSON object?
We can use python-jsonschema-objects which is built on top of jsonschema.The python-jsonschema-objects provide an automatic class-based binding to JSON schemas for use in Python.We have a sample json schema as followsschema = '''{ "title": "Example Schema", "type": "object", "properties": { "firstName": { "type": "string" }, "lastName": { ...
Read MoreHow we can instantiate different python classes dynamically?
To instantiate the python class, we need to get the class name first. This is achieved by following codedef get_class( kls ): parts = kls.split('.') module = ".".join(parts[:-1]) m = __import__( module ) for comp in parts[1:]: m = getattr(m, comp) return mm is the classWe can instantiate this class as followsa = m() b = m(arg1, arg2) # passing args to the constructor
Read MoreReply to user text using Python
You can solve this problem by using if-elif-else statements. And to make it like, it will ask for a valid option until the given option is on the list, we can use while loops. When the option is valid, then break the loop, otherwise, it will ask for the input repeatedly.You should take the input as an integer, for that you need to typecast the input to an integer using int() method.ExamplePlease check the code to follow the given points.print("Come-on in. Need help with any bags?") while True: # loop is used to take option until it is not valid. ...
Read MoreHow does Python class inherit objects?
In Python 2.x there are two styles of classes depending on the presence or absence of a built-in type as a base-class −‘Old style’ or "Classic" style classes: they have no built-in type as a base class −>>> class OldFoo: # no base class ... pass >>> OldFoo.__bases__ ()"New" style classes: they have a built-in type as a base class meaning that, directly or indirectly, they have object as a base class −>>> class NewFoo(object): # directly inherit from object ... pass >>> NewFoo.__bases__ (, )In Python 3.x however, only ...
Read MoreHow I can check if class attribute was defined or derived in given class in Python?
The code below shows the if the attribute 'foo' was defined or derived in the classes A and B.Exampleclass A: foo = 1 class B(A): pass print A.__dict__ #We see that the attribute foo is there in __dict__ of class A. So foo is defined in class A. print hasattr(A, 'foo') #We see that class A has the attribute but it is defined. print B.__dict__ #We see that the attribute foo is not there in __dict__ of class B. So foo is not defined in class B print hasattr(B, 'foo') #We see ...
Read MoreHow do I enumerate functions of a Python class?
The following code prints the list of functions of the given class as followsExampleclass foo: def __init__(self): self.x = x def bar(self): pass def baz(self): pass print (type(foo)) import inspect print(inspect.getmembers(foo, predicate=inspect.ismethod))OutputThe output is [('__init__', ), ('bar', ), ('baz', )]
Read MoreWhat is the difference between old style and new style classes in Python?
In Python 2.x there's two styles of classes depending on the presence or absence of a built-in type as a base-class −"classic" style or old style classes have no built-in type as a base class: >>> class OldSpam: # no base class ... pass >>> OldSpam.__bases__ ()"New" style classes: they have a built-in type as a base class meaning that, directly or indirectly, they have object as a base class −>>> class NewSpam(object): # directly inherit from object ... pass >>> NewSpam.__bases__ (, ) >>> class IntSpam(int): ...
Read MoreHow data hiding works in Python Classes?
Data hidingIn Python, we use double underscore before the attributes name to make them inaccessible/private or to hide them.The following code shows how the variable __hiddenVar is hidden.Exampleclass MyClass: __hiddenVar = 0 def add(self, increment): self.__hiddenVar += increment print (self.__hiddenVar) myObject = MyClass() myObject.add(3) myObject.add (8) print (myObject.__hiddenVar)Output 3 Traceback (most recent call last): 11 File "C:/Users/TutorialsPoint1/~_1.py", line 12, in print (myObject.__hiddenVar) AttributeError: MyClass instance has no attribute '__hiddenVar'In the above program, we tried to access hidden variable outside the class using object and it threw an ...
Read MoreWhat does the cmp() function do in Python Object Oriented Programming?
The cmp() functionThe cmp(x, y) function compares the values of two arguments x and y −cmp(x, y)The return value is −A negative number if x is less than y.Zero if x is equal to y.A positive number if x is greater than y.The built-in cmp() function will typically return only the values -1, 0, or 1. However, there are other places that expect functions with the same calling sequence, and those functions may return other values. It is best to observe only the sign of the result.>>> cmp(2, 8) -1 >>> cmp(6, 6) 0 >>> cmp(4, 1) 1 >>> cmp('stackexchange', ...
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