HTTP Status Code for newbies

If you are having hard time understanding or remembering HTTP codes then this article is for you.

credit - monkeyuser.com

301 Moved Permanently

The requested resource has been assigned a new permanent URI and any future references to this resource SHOULD use one of the returned URIs. Clients with link editing capabilities ought to automatically re-link references to the Request-URI to one or more of the new references returned by the server, where possible. This response is cacheable unless indicated otherwise.
The new permanent URI SHOULD be given by the Location field in the response. Unless the request method was HEAD, the entity of the response SHOULD contain a short hypertext note with a hyperlink to the new URI(s).

305 Use Proxy

The requested resource MUST be accessed through the proxy given by the Location field. The Location field gives the URI of the proxy. The recipient is expected to repeat this single request via the proxy. 305 responses MUST only be generated by origin servers.

307 Temporary Redirect

The requested resource resides temporarily under a different URI. Since the redirection MAY be altered on occasion, the client SHOULD continue to use the Request-URI for future requests. This response is only cacheable if indicated by a Cache-Control or Expires header field.

400 Bad Request

The request could not be understood by the server due to malformed syntax. The client SHOULD NOT repeat the request without modifications.

404 Not Found

The server has not found anything matching the Request-URI. No indication is given of whether the condition is temporary or permanent. The 410 (Gone) status code SHOULD be used if the server knows, through some internally configurable mechanism, that an old resource is permanently unavailable and has no forwarding address. This status code is commonly used when the server does not wish to reveal exactly why the request has been refused, or when no other response is applicable.

408 Request Timeout

The client did not produce a request within the time that the server was prepared to wait. The client MAY repeat the request without modifications at any later time.

413 Request Entity Too Large

The server is refusing to process a request because the request entity is larger than the server is willing or able to process. The server MAY close the connection to prevent the client from continuing the request.
If the condition is temporary, the server SHOULD include a Retry- After header field to indicate that it is temporary and after what time the client MAY try again.

417 Expectation Failed

The expectation given in an Expect request-header field (see section 14.20) could not be met by this server, or, if the server is a proxy, the server has unambiguous evidence that the request could not be met by the next-hop server.

500 Internal Server Error

The server encountered an unexpected condition which prevented it from fulfilling the request.

How to shorten the bash shell prompt

So sometimes it happens that you are working on command terminal and you navigate inside a directory then again in inner directory and so on until half of the screen width is filled with prompt string. Example below....

rana@Brahma: dir1/dir2/dir3/dir4/dir5/dir6/dir7/dir8 $ ls 

Now I want to display just the last directory in terminal prompt string so that I am left with enough width space to execute length commands.

For this We need to change the prompt string from .bashrc file. Below are the steps -

1. Go to your home directory.
2. Open .bashrc file.
3. Search for string 'PS1'. To search quick open the file in vi and type /PS1 and hit enter.
4. now you will find below code. (or similar to it) [ I am working on Ubuntu 16.04]

if [ "$color_prompt" = yes ]; then
    PS1='${debian_chroot:+($debian_chroot)}\[\033[01;32m\]\u@\h\[\033[00m\]:\[\033[01;34m\]\w\[\033[00m\]\$ '
else
    PS1='${debian_chroot:+($debian_chroot)}\u@\h:\w\$ '
fi

5. Replace the 'w' (highlighted in blue color) with capital W. So your new code will be.

if [ "$color_prompt" = yes ]; then
    PS1='${debian_chroot:+($debian_chroot)}\[\033[01;32m\]\u@\h\[\033[00m\]: \[\033[01;34m\]\W\[\033[00m\]\$ '
else
    PS1='${debian_chroot:+($debian_chroot)}\u@\h:\w\$ '
fi

6. Restart the terminal and navigate inside any directory. You will see just the last directory in teminal prompt.

rana@Brahma: dir8$

Happy Learning.

 

How to hide pages on google sites

Sometimes you might required to hide some pages from public views in Google sites. Or you may want to delete the page but then you might use same page again so you decided to save the page as draft temporarily.

Here is the step by step process to do so.

- Login to your account. Open the google site.
- Open any page. Click on the settings button on top right corner.

- Look for sharing and permission menu item. Click on it.

- on next page, click on 'Turn page level permission on'.

- Now select any page you want to hide or save as draft.
- Change the permission settings to desired value.

How to use custom UserModel in django

In previous article we learned how to use django authentication in your application. But sometimes it may happen that default user model of django does not fit your requirement. You may want to add more fields to it. Now there are multiple ways to do it.

1. Use proxy model. No new model is created.
2. Use one-to-one relationship and create another model.
3. Create your own user model and use default authentication system.
4. Create your own user model and create your own authentication system.

Previous article - http://www.newbie42.com/2016/09/implementing-authentication-in-django.html

We will be learning 3rd method here.

Note : This needs to be done before performing any migration.

- First create the custom user model and custom user manager.

from django.db import models
from django.contrib.auth.models import AbstractBaseUser, BaseUserManager
from django.utils import timezone
from django.db.models import Max

class MyUserManager(BaseUserManager):
use_in_migrations = True
def create_user(self,login, parent_type, last_name, first_name, password):
return create_superuser(self,login, parent_type, last_name, first_name, password)

def create_superuser(self,login, parent_type, last_name, first_name, password):
maxx = self.model.objects.all().aggregate(Max('sys_id'))
if maxx["sys_id__max"] is None:
maxx["sys_id__max"] = 0
user = self.model(
                 sys_id = maxx["sys_id__max"] + 1,
                 login = login,
                 parent_type = parent_type,
                 last_name = last_name,
                 first_name = first_name,
                 display_name = last_name + " " + first_name,
                 created_when = timezone.now()
                 )
user.set_password(password)
user.save(using=self._db)
# no difference here...actually can set is_admin = True or something like that.
return user

class UserModel(AbstractBaseUser):
# custom user class

sys_id = models.BigIntegerField(primary_key=True, blank=True)
last_name = models.CharField(null=False, blank=False, max_length=40)
first_name = models.CharField(max_length=40, null=False, blank=False)
display_name = models.CharField(max_length=80, unique=True, null=False, blank=True)
login = models.CharField(max_length=40, unique=True, null=False, blank=False)
authentication_method = models.CharField(max_length=80, null=True, blank=True)
access_valid_start = models.DateTimeField(null=True, blank=True)
access_valid_end = models.DateTimeField(null=True, blank=True)
notes = models.CharField(max_length=2048, null=True, blank=True)
is_active = models.BooleanField(default=True)

objects = MyUserManager()

USERNAME_FIELD = "login"
# REQUIRED_FIELDS must contain all required fields on your User model, 
# but should not contain the USERNAME_FIELD or password as these fields will always be prompted for.
REQUIRED_FIELDS = [ 'last_name', 'first_name']

class Meta:
app_label = "appname"
db_table = "Users"

def __str__(self):
return self.display_name

def get_full_name(self):
return self.display_name

def get_short_name(self):
return self.last_name


- Now in your settings.py file add this line. It will tell your application that you have to use your custom model for authentication instead of default one.

AUTH_USER_MODEL = 'accounts.UserModel'

- Write your login/logout functions just like in previous article.
-

Implementing authentication in Django

Django - 1.9
Python - 3.4

To implement the authentication in django follow these steps.

- First complete the initial migration so that initial tables are created in DB.
- Create superuser.
- Login to admin module using the credentials created in step above.
- Create another user which might be admin 'staff' member or not.
- Edit your url.conf file and add the urls corresponding to login and logout.
 [replace appname with your app's name in code below]

    url(r'^$', views.index, name='index'),
    url(r'^login/$', views.appname_login, name='appname_login'),
    url(r'^logout/$', views.appname_logout, name='appname_logout'), 


- Create login, logout and index functions in your view.py file

from django.shortcuts import render, redirect
from django.contrib.auth.decorators import login_required
from django.contrib.auth import authenticate, login, logout
from django.core.urlresolvers import reverse


@login_required(login_url='/appname/login/')
def index(request):
    print(request.user)
    context = {}
    context["user"] = request.user
    return render(request, "appname/index.html", context)



def tenant_login(request):
    context = {}
    if request.method == "GET":
        if "next" not in request.GET:
            context["next"] = "/appname/"
        else:
            context["next"] = request.GET["next"]
        return render(request, "appname/login.html", context)
    else:
        username = request.POST["username"]
        password = request.POST["password"]
        next_url = request.POST["next"]
        user = authenticate(username=username, password=password)
        if user is not None:
            if user.is_active:
                login(request, user)
                return redirect(next_url, args=(),kwargs={})
            else:
                context["message"] = "User is not active"
        else:
            context["message"] = "Invalid username or password"
        return render(request, "appname/login.html", context)


@login_required(login_url='/appname/login/')
def tenant_logout(request):
    logout(request)
    url = reverse("appname:appname_login")
    return redirect(url, args=(),kwargs={})

- Create login.html file in template directory.

   <form method="post" action="{% url "appname:appname_login" %}">
        {% csrf_token %}
        <input type="text" name="next" hidden="" value="{{next}}">         
        <input type="text" name="username"> 
        <input type="password" name="password">
        <input type="submit" name="submit" value="Log In">
    </form>
    {{message}}


- Inside your index.html file

   {% if user.is_authenticated  %}
    {{user.first_name}}
    <a href="{% url "tenant:tenant_logout" %}">Logout</a>
    {% endif %}

- Run the python server. Goto localhost:8000/appname/.
- In view file you can see that 'index' method uses login_required decorator, if you are not logged in than you will be redirected to login page.
- When you are redirected to login page from any xyz page then a url parameter is added to url which tells where to redirect on successful login. Observe the url in address bar when you are redirected to login page.
- Enter the username and password of the user created in a step above. Log in.
- You will redirected to index page. If user is authenticated (if user is not AnonymousUser) then user's first name and logout link is displayed otherwise not.
- Clicking logout will logout you from the application and try to redirect to index page. but since index page requires login you will be redirected to login page.
- You can print user's full name in index template because you have full access to user object. Use {{user.get_full_name}} or {{user.first_name}} in template.


Let me know if you face any issues in this.

Pretty print json using comman line

1.  cat FileName.json | python -m json.tool

2.  cat FileName.json~ | jq ''

Bonus - colors and multiple options.

Output -

{

  "Apply_Data": "",

  "Message": "Invalid Token or Username-Password combination.",

  "Code": 403

}

3.

echo '{"foo": "bar"}' | python -m json.tool | pygmentize -g

Bonus - Pretty print with syntax highlighting.

Ubuntu 16.04 new features

Ubuntu 16.04 is about to release on 23rd of April 2016. Ubuntu fans might be exited about the latest features coming to this release. Here is the list of all such features.

Official mascot of Ubuntu 16.04

1. Online searches have been disabled from unity search results. Now you will not see any more Amazon suggestions.

2. Ubuntu software center has been removed as it was very heavy.

3. 'apt-get' has been replaced with 'apt' only. This command is used in Debian systems. 

4. Unity Launcher can be moved to bottom of the screen.

5. Default support for ZFS file system.

6. Linux Kernel 4.4 , Mozilla Thunderbird updated to 45.0,  Docker 1.10 and much more...

Me right now...