Installing Python Third Party Libraries

From previous tutorials of this course, you must have gathered some idea about networking and stuff. Now it's time for us to get our hands dirty. But before that, do you know what are python libraries or python modules? Well, technically a module is simply a Python source file, which can expose classes, functions and global variables. A Python module can be used or imported in another python module. If you are new to python, learn python on Studytonight.

You might think Why do we need modules? Using Modules increase code reusability and helps in easy maintenance of programs. For example: Suppose you are writing a program which is very big. As your program gets longer, you may want to split it into several files for easier maintenance. You may also want to reuse the function definition which you created for one program into another without writing or coping the function again. To support this, Python has a way to put definitions in a file and use them in a script. Such a file is called a module.

Let's take an example of a module for adding numbers: Assume add.py to be a module for adding two numbers.

# Addition Module

def add(a,b): #add two numbers 'a' and 'b'
    c = a + b
    return c

add.py

Now suppose we are creating a calc.py program and we need a function to add 2 numbers. We can simply import our add.py module(as import add) in calc.py for this purpose.

Note: Both the files should be in the same directory for this purpose.

Now to call the add() method, from the module add.py, we do → ModuleName.MethodName after successfully importing the module into the program.

>>> import add
>>> add.add(9,8)
>>> add.add(9.7,5)

17 14.7

The limitless power of python does not end with this. You can import python modules according to your convenience and need. We will be dicussing two ways for installing external python modules to your system, they are:

• using pip
• by downloading package indepedently from third party.

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Installing packages using pip

pip is the preferred installer program. Starting with Python 2.7.9, it is included as default with the Python binary installers i.e Python version > 3.0 will have pre-installed pip installer in it.

For versions < 2.7.9 you have to install pip manually. To install pip in these version follow the below steps:

• For Debian(Ubuntu/Kali etc) distribution of linux just use:

  $ sudo apt-get install python-pip

• For Windows user:

  Download get-pip.py from here. Then, run it from the command prompt:

  python get-pip.py

  You possibly need an administrator command prompt to do this.

• To check for proper installation of pip type:

  pip -V

If the version of pip is displayed than you are good to go. Now you are ready to download python packages using pip. To download any package using pip :

pip install package_name
#Note: Use sudo if you are using linux as non-root user

For example: Say for installing a package named bs4(Beautiful Soup) using pip:

~$ sudo pip install bs4

For detailed knowledge and further problems regarding pip installation follow the official documentation→ https://docs.python.org/2/installing/index.html

Now, the Python Packaging Index is a public repository of open source licensed packages made available for use by other Python users. So, there will be times when some of the required packages cannot be directly downloaded using pip. In that case you need to download and install the required package by third party providers.

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Installing third party python packages

• For this purpose, download the compressed (tar.gz or .zip) file for the required package.
• Extract the compressed file (to extract tar.gz file in linux use, tar -xvzf package_name.tar.gz).
• Now, go to the extracted package directory using.

  cd package_name

• Now to install the package simply run this on command line

  python setup.py install

Some sources to download third party libraries are:

https://github.com

https://pypi.python.org/pypi

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