Super Javascript Class

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The Python super () method allows you to access the methods of a parent class inside a child class. This helps reduce repetition in the code. super () takes no arguments. One of the main characteristics of object oriented programming languages ‚Äã‚Äãlike Python is inheritance. Inheritance occurs when a new class uses code from another class to create the new class.

When you inherit classes, you can have access to methods from a parent class. This is where the super () function comes in .

This tutorial will discuss the basics of inheritance in Python with examples. Next, we’ll talk about how to use the super () function for values ‚Äã‚Äãand methods to inherit from a parent class.

What is Super Python?

The super - Python () method allows you to access methods in a parent class. You can think of super () as a way of display methods in the class from which another class is inherited

Here is the syntax for the super () method.

The super () method takes no arguments. You specify the method you want to inherit after the super () method. The previous Python class inherits values ‚Äã‚Äãfrom the __init __ () method of the food class. We call super () class method to the values ‚Äã‚Äãinherit from the food class.

Python inheritance refers to a process in which a new class uses code from an existing class to define the structure of the new one class

One way to think about inheritance is to look at how children inherit characteristics from their children. parents. A child can have the same hair color as their parents and even inherit the last name from their parents.

In Python, there are two types of classes:.

  • Classes for children (or "Subclasses ") Inherit methods and variables. Child classes are sometimes called sister classes
  • Main classes (or "base classes") are classes whose values ‚Äã‚Äãcan be inherited

super () Python:. Inherit from __init __ ()

Suppose we create a bank account system that keeps track of the credentials of people who hold an account with a bank, we want to create a class that stores the data for account verification We could do it using this code:.

This code creates a current account project.

Now, suppose we want to create a class that stores the project for children’s bank accounts, which we’ll call ChildAccount. the class should be based on the CheckingAccount class we defined earlier. To do this we can use the super () function.

super () allows you to access the methods of a parent class within a child class.

In our example, our parent class, it’s called CheckingAccount and our child class is called ChildAccount. CheckingAccount creates the project for a bank account and ChildAccount inherits the values ‚Äã‚Äãfrom CheckingAccount to create its own class.

Now, suppose we want the ChildAccount class to inherit the values ‚Äã‚Äãstored in our CheckingAccount. But we also want this account to store a new value called is_child, which should be True by default.

We could create our new ChildAccount class using this code:

This code creates a project for our new ChildAccount class. We use the super () method to inherit the name and values ‚Äã‚Äãof the Balance CheckingAccount class. We specify CheckingAccount the parent class in parentheses in the first line of our class.

This shows that super () allows you to inherit all values ‚Äã‚Äãfrom another class. But, in our code, we also declared a new value called is_child . This value will not be accessible to any ChildAccount because it has been declared in the ChildAccount class

to create an instance of our class for a child account holder, we can use this code:

Our code returns:

We have declared an instance of ChildAccount class assigned to the Python variables lynn . lynn is a class object because we were declaring the value of lynn using an object.

Lynn’s account has $ 200 and the value of is_child is true by default. Next, we printed name, balance, is_child values ‚Äã‚Äãassociated with Lynn aunt of acc . We print these values ‚Äã‚Äãto the console using the print () Python method.

Why we inherited name and balance from the CheckingAccount class, we were able to use them in our code. However, Lynn’s account also has a set of values ‚Äã‚Äãfor is_child, which is set to True by default for all instances of ChildAccount.

super () Python: inherit Methods

super () allows classes to inherit using single level inheritance - a class inheriting from a parent class. Or you can use super () with multilevel inheritance . For this example, we will focus on single level inheritance with super ().

In our previous example, we used super () to Inherit the values ‚Äã‚Äãstored in the CheckingAccount class and make them available to the ChildAccount class. But what if we wanted to inherit from a method and modify its response

Either class back to our CheckingAccount go from start:

In this class we have defined the design for the values the class should store - name and balance. We have defined a method called Checkbalance () which allows a user to check their balance

Now suppose we want to make Checkbalance () accessible to our ChildAccount. We also want to print a message saying "You have a child account!" It appears before the user’s balance is printed to the console.

We can access our inherited methods like this:

We have declared a new version of the Checkbalance () method ChildAccount class. This first version displays "You have a child account!" to the console, so our super () code uses for the Checkbalance () of the mother class .

In this case, when super (). Checkbalance () is executed, the Checkbalance () function of CheckingAccount class is executed. Which displays the user’s balance on the console

Now we’ll try to access our Checkbalance () method on behalf of Lynn.

Our code returns:

When we call lynn.checkBalance () method, the code in our ChildAccount.checkBalance () method is race , the super object executes the code in the CheckingAccount.checkBalance () method.

The super () function allows us to use parent methods, while still being able to override those methods in our child classes.

Conclusion

The Python super () function allows you to inherit methods from a class parent. The super () function helps you write more readable code because you can reuse code from existing functions.

This tutorial has discussed, with examples, how to use the super () function. inherit values ‚Äã‚Äãand methods from a parent class. You are now equipped with the knowledge to start using the super () function like a Python pro!

For more resources on Python programming, read our Python Learning Guide .

👻 Read also: what is the best laptop for engineering students?

Super Javascript Class iat: Questions

iat

InsecurePlatformWarning: A true SSLContext object is not available. This prevents urllib3 from configuring SSL appropriately

3 answers

Tried to perform REST GET through python requests with the following code and I got error.

Code snip:

import requests
header = {"Authorization": "Bearer..."}
url = az_base_url + az_subscription_id + "/resourcegroups/Default-Networking/resources?" + az_api_version
r = requests.get(url, headers=header)

Error:

/usr/local/lib/python2.7/dist-packages/requests/packages/urllib3/util/ssl_.py:79: 
          InsecurePlatformWarning: A true SSLContext object is not available. 
          This prevents urllib3 from configuring SSL appropriately and may cause certain SSL connections to fail. 
          For more information, see https://urllib3.readthedocs.org/en/latest/security.html#insecureplatformwarning.
  InsecurePlatformWarning

My python version is 2.7.3. I tried to install urllib3 and requests[security] as some other thread suggests, I still got the same error.

Wonder if anyone can provide some tips?

334

Answer #1

The docs give a fair indicator of what"s required., however requests allow us to skip a few steps:

You only need to install the security package extras (thanks @admdrew for pointing it out)

$ pip install requests[security]

or, install them directly:

$ pip install pyopenssl ndg-httpsclient pyasn1

Requests will then automatically inject pyopenssl into urllib3


If you"re on ubuntu, you may run into trouble installing pyopenssl, you"ll need these dependencies:

$ apt-get install libffi-dev libssl-dev

Super Javascript Class iat: Questions

iat

Dynamic instantiation from string name of a class in dynamically imported module?

3 answers

In python, I have to instantiate certain class, knowing its name in a string, but this class "lives" in a dynamically imported module. An example follows:

loader-class script:

import sys
class loader:
  def __init__(self, module_name, class_name): # both args are strings
    try:
      __import__(module_name)
      modul = sys.modules[module_name]
      instance = modul.class_name() # obviously this doesn"t works, here is my main problem!
    except ImportError:
       # manage import error

some-dynamically-loaded-module script:

class myName:
  # etc...

I use this arrangement to make any dynamically-loaded-module to be used by the loader-class following certain predefined behaviours in the dyn-loaded-modules...

222

Answer #1

You can use getattr

getattr(module, class_name)

to access the class. More complete code:

module = __import__(module_name)
class_ = getattr(module, class_name)
instance = class_()

As mentioned below, we may use importlib

import importlib
module = importlib.import_module(module_name)
class_ = getattr(module, class_name)
instance = class_()

Super Javascript Class iat: Questions

iat

How to get all of the immediate subdirectories in Python

3 answers

I"m trying to write a simple Python script that will copy a index.tpl to index.html in all of the subdirectories (with a few exceptions).

I"m getting bogged down by trying to get the list of subdirectories.

184

Answer #1

import os
def get_immediate_subdirectories(a_dir):
    return [name for name in os.listdir(a_dir)
            if os.path.isdir(os.path.join(a_dir, name))]

JSON datetime between Python and JavaScript

4 answers

kevin By kevin

I want to send a datetime.datetime object in serialized form from Python using JSON and de-serialize in JavaScript using JSON. What is the best way to do this?

403

Answer #1

You can add the "default" parameter to json.dumps to handle this:

date_handler = lambda obj: (
    obj.isoformat()
    if isinstance(obj, (datetime.datetime, datetime.date))
    else None
)
json.dumps(datetime.datetime.now(), default=date_handler)
""2010-04-20T20:08:21.634121""

Which is ISO 8601 format.

A more comprehensive default handler function:

def handler(obj):
    if hasattr(obj, "isoformat"):
        return obj.isoformat()
    elif isinstance(obj, ...):
        return ...
    else:
        raise TypeError, "Object of type %s with value of %s is not JSON serializable" % (type(obj), repr(obj))

Update: Added output of type as well as value.
Update: Also handle date

What blocks Ruby, Python to get Javascript V8 speed?

4 answers

Are there any Ruby / Python features that are blocking implementation of optimizations (e.g. inline caching) V8 engine has?

Python is co-developed by Google guys so it shouldn"t be blocked by software patents.

Or this is rather matter of resources put into the V8 project by Google.

260

Answer #1

What blocks Ruby, Python to get Javascript V8 speed?

Nothing.

Well, okay: money. (And time, people, resources, but if you have money, you can buy those.)

V8 has a team of brilliant, highly-specialized, highly-experienced (and thus highly-paid) engineers working on it, that have decades of experience (I"m talking individually – collectively it"s more like centuries) in creating high-performance execution engines for dynamic OO languages. They are basically the same people who also created the Sun HotSpot JVM (among many others).

Lars Bak, the lead developer, has been literally working on VMs for 25 years (and all of those VMs have lead up to V8), which is basically his entire (professional) life. Some of the people writing Ruby VMs aren"t even 25 years old.

Are there any Ruby / Python features that are blocking implementation of optimizations (e.g. inline caching) V8 engine has?

Given that at least IronRuby, JRuby, MagLev, MacRuby and Rubinius have either monomorphic (IronRuby) or polymorphic inline caching, the answer is obviously no.

Modern Ruby implementations already do a great deal of optimizations. For example, for certain operations, Rubinius"s Hash class is faster than YARV"s. Now, this doesn"t sound terribly exciting until you realize that Rubinius"s Hash class is implemented in 100% pure Ruby, while YARV"s is implemented in 100% hand-optimized C.

So, at least in some cases, Rubinius can generate better code than GCC!

Or this is rather matter of resources put into the V8 project by Google.

Yes. Not just Google. The lineage of V8"s source code is 25 years old now. The people who are working on V8 also created the Self VM (to this day one of the fastest dynamic OO language execution engines ever created), the Animorphic Smalltalk VM (to this day one of the fastest Smalltalk execution engines ever created), the HotSpot JVM (the fastest JVM ever created, probably the fastest VM period) and OOVM (one of the most efficient Smalltalk VMs ever created).

In fact, Lars Bak, the lead developer of V8, worked on every single one of those, plus a few others.

Django Template Variables and Javascript

4 answers

When I render a page using the Django template renderer, I can pass in a dictionary variable containing various values to manipulate them in the page using {{ myVar }}.

Is there a way to access the same variable in Javascript (perhaps using the DOM, I don"t know how Django makes the variables accessible)? I want to be able to lookup details using an AJAX lookup based on the values contained in the variables passed in.

256

Answer #1

The {{variable}} is substituted directly into the HTML. Do a view source; it isn"t a "variable" or anything like it. It"s just rendered text.

Having said that, you can put this kind of substitution into your JavaScript.

<script type="text/javascript"> 
   var a = "{{someDjangoVariable}}";
</script>

This gives you "dynamic" javascript.

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