Showing posts with label python_2_7. Show all posts
Showing posts with label python_2_7. Show all posts

Saturday, July 18, 2015

Learn what is python method mangling and variable mangling

While I was studying python, there are some unique word, mangling that caught my attention. There are two mangling, the method and the variable. But first, let's take a look what is mangling in python. From the official pep 8 documentation.

  If your class is intended to be subclassed, and you have attributes that you do not want subclasses to use, consider naming them with double leading underscores and no trailing underscores. This invokes Python's name mangling algorithm, where the name of the class is mangled into the attribute name. This helps avoid attribute name collisions should subclasses inadvertently contain attributes with the same name.

  Python mangles these names with the class name: if class Foo has an attribute named __a , it cannot be accessed by Foo.__a . (An insistent user could still gain access by calling Foo._Foo__a .) Generally, double leading underscores should be used only to avoid name conflicts with attributes in classes designed to be subclassed.

Okay, with that said and explained, let's hop into the code. We will create two class, parent and child class and both sharing the same method and same variable.

 $ cat  
 class Parent(object):  
   __name = "John Smith"  
   def __init__(self):  
     self.__alive = False  
     self.__parentAlive = False  
   def __show_age(self):  
     print "65"  
 class Child(Parent):  
   __name = "John Smith Junior"  
   def __init__(self):  
     super(Child, self).__init__()  
     self.__alive = True  
     self.__childAlive = True  
   def __show_age(self):  
     print "34"  

now import this module into python interpreter and understand how mangling works.

 $ python  
 Python 2.7.10 (default, Jun 1 2015, 16:21:46)   
 [GCC 4.9.2] on linux2  
 Type "help", "copyright", "credits" or "license" for more information.  
 >>> from mangle import Child  
 >>> johnny = Child()  
 >>> dir(johnny)  
 ['_Child__alive', '_Child__childAlive', '_Child__name', '_Child__show_age', '_Parent__alive', '_Parent__name', '_Parent__parentAlive', '_Parent__show_age', '__class__', '__delattr__', '__dict__', '__doc__', '__format__', '__getattribute__', '__hash__', '__init__', '__module__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__', '__weakref__']  
 >>> johnny._Child__alive  
 >>> johnny._Child__name  
 'John Smith Junior'  
 >>> johnny._Child__show_age()  
 >>> johnny._Parent__alive  
 >>> johnny._Parent__name  
 'John Smith'  
 >>> johnny._Parent__show_age()  

So with this, it should be clear that the attributes that live in the python object will prepend with an underscore and the class name with the variable. Same wise applicable to the method name too.

Sunday, July 5, 2015

Check out what is Python package

It's been a while I learn python and today, I would like to check out what is python package. These two reference give python package definition pretty clear.

Packages are a way of structuring Python's module namespace by using "dotted module names". For example, the module name ‘A.B’ designates a submodule named ‘B’ in a package named ‘A’. Just like the use of modules saves the authors of different modules from having to worry about each other's global variable names, the use of dotted module names saves the authors of multi-module packages like NumPy or the Python Imaging Library from having to worry about each other's module names. 

and from learn python org

Packages are namespaces which contain multiple packages and modules themselves. They are simply directories, but with a twist. 
Each package in Python is a directory which MUST contain a special file called This file can be empty, and it indicates that the directory it contains is a Python package, so it can be imported the same way a module can be imported. 

If you come from java background, essentially java package are directories until you create a class. In python, for that directory, you need to create a unique empty file call which denote this is a python package.

So something like


The above file structure is from github project.We have a python package router_statistics with a module Then we have a test python package and a test module

Pretty neat :) That's all for this light learning experience.

Saturday, May 23, 2015

Learning oauth2 with linkedin using python script

Today, we are going to learn oauth2 with linkedin using python. It's a very simple and easy task. Let's install the necessary library dependency. In debian, you just will need to install these two dependency packages, that is python-requests-oauthlib and python-oauthlib.

If you want to be sure the module are installed, you can start a python interactive shell, read below:

 user@localhost:~$ python  
 Python 2.7.9 (default, Apr 29 2015, 18:34:06)   
 [GCC 4.9.2] on linux2  
 Type "help", "copyright", "credits" or "license" for more information.  
 >>> from requests_oauthlib import OAuth2Session  
 >>> from requests_oauthlib.compliance_fixes import linkedin_compliance_fix  

Looks good, there is no error. If you do not have apt package manager, you can alternatively use pip to install, such as the following:

 user@localhost:~$ sudo pip install requests requests_oauthlib  
 Downloading/unpacking requests  
  Downloading requests-2.7.0.tar.gz (451kB): 451kB downloaded  
  Running egg_info for package requests  
 Downloading/unpacking requests-oauthlib  
  Downloading requests-oauthlib-0.5.0.tar.gz (54kB): 54kB downloaded  
  Running egg_info for package requests-oauthlib  
 Downloading/unpacking oauthlib>=0.6.2 (from requests-oauthlib)  
  Downloading oauthlib-0.7.2.tar.gz (106kB): 106kB downloaded  
  Running egg_info for package oauthlib  
 Installing collected packages: requests, requests-oauthlib, oauthlib  
  Running install for requests  
  Running install for requests-oauthlib  
  Running install for oauthlib  
 Successfully installed requests requests-oauthlib oauthlib  
 Cleaning up...  

Okay, so you are set, now let's create a python script now for the oauth2.

1:  #!/usr/bin/python  
4:  # Credentials you get from registering a new application  
5:  client_id = '***********'  
6:  client_secret = '**********'  
8:  # OAuth endpoints given in the LinkedIn API documentation  
9:  authorization_base_url = ''  
10:  token_url = ''  
12:  from requests_oauthlib import OAuth2Session  
13:  from requests_oauthlib.compliance_fixes import linkedin_compliance_fix  
15:  linkedin = OAuth2Session(client_id, redirect_uri='')  
16:  linkedin = linkedin_compliance_fix(linkedin)  
18:  # Redirect user to LinkedIn for authorization  
19:  authorization_url, state = linkedin.authorization_url(authorization_base_url)  
20:  print 'Please go here and authorize,', authorization_url  
22:  # Get the authorization verifier code from the callback url  
23:  redirect_response = raw_input('Paste the full redirect URL here:')  
25:  linkedin.fetch_token(token_url, client_secret=client_secret, authorization_response=redirect_response)  
27:  # Fetch a protected resource, i.e. user profile  
28:  r = linkedin.get('')  
29:  print r.content  

There are basically two variable value you need to change, client_id and client_secret. You should be able to find these two variable in your linkedin developer application page. Once you login to your developer login page, you should be able to locate these two parameters. Note that, because of privacy of credential, I have remove them all, but you should get be able to find out. Note also you need to provide a redirect url, as seen here, it is match with what it is found in the script.

Now, we are almost ready. If you execute this script in the terminal,

 user@localhost:~$ python  
 Please go here and authorize,**********&redirect_uri=http%3A%2F%2F127.0.0.1&state=*************  
 Paste the full redirect URL here:******************************************************************************************************************************************&state=***************  
 <?xml version="1.0" encoding="UTF-8" standalone="yes"?>  
  <headline>Software Engineer</headline>  

So you should copy the first link in the script output into the browser, a linkedin authorization page will be loaded, you should authorized it and the next url, copy and paste back into the terminal. Voila, you can use the token to start use various linkedin api.