Introduction to Python

1.1
CHAPTER
1
INTRODUCTION TO PYTHON
After reading this chapter, the reader will be able to
• Understand the chronology of Python
• Appreciate the importance and features of Python
• Discover the areas in which Python can be used
• Install Anaconda
INTRODUCTION
Art is an expression of human creative skill, hence programming is an art. The
choice of programming language is, therefore, important. This book introduces
Python, which will help you to become a great artist. A. J. Perlis, who was a
professor at the Purdue University, and who was the recipient of the first Turing
award, stated
“A language that doesn’t affect the way you think about programming is
not worth knowing.”
Python is worth knowing. Learning Python will not only motivate you to do
highly complex tasks in the simplest manners but will also demolish the myths
of conventional programming paradigms. It is a language which will change the
way you program and hence look at a problem.
Python is a strong, procedural, object-oriented, functional language crafted in the
late 1980s by Guido Van Rossum. The language is named after Monty Python, a
comedy group. The language is currently being used in diverse application
domains. These include software development, web development, Desktop GUI
development, education, and scientific applications. So, it spans almost all the
facets of development. Its popularity is primarily owing to its simplicity and
robustness, though there are many other factors too which are discussed in the

1.2
chapters that follow.
There are many third party modules for accomplishing the above tasks. For
example Django, an immensely popular Web framework dedicated to clean and
fast development, is developed on Python. This, along with the support for
HTML, E-mails, FTP, etc., makes it a good choice for web development.
Third party libraries are also available for software development. One of the
most common examples is Scions, which is used for build controls. When joined
with the inbuilt features and support, Python also works miracles for GUI
development and for developing mobile applications, e.g., Kivy is used for
developing multi-touch applications.
Python also finds its applications in scientific analysis. SciPy is used for
Engineering and Mathematics, and IPython is used for parallel computing. Those
of you working in statistics and machine learning would find some of these
libraries extremely useful and easy to use. SciPy provides
MATLABMATLABMATLAB like features and can be used for processing
multidimensional arrays. Figure 1.1 summarizes the above discussion.
FIGURE 1.1 Some of the applications of Python
This chapter introduces the Python programming language. The chapter has been
organized as follows. Section 1.2 discusses the features of Python, Section 1.3
discusses the paradigms and Section 1.4 discusses the development and uses.
The installation of Anaconda has been introduced in Section 1.5. The last section
concludes the chapter.
FEATURES OF PYTHON

1.2.1
1.2.2
1.2.3
1.2.4
As stated earlier, Python is a simple but powerful language. Python is portable. It
has built-in object types, many libraries and is free. This section briefly discusses
the features and strengths of Python.
Easy
Python is easy to learn and understand. As a matter of fact, if you are from a
programming background you will find it elegant and uncluttered. The removal
of braces and parentheses makes the code short and sweet. Also, some of the
tasks in Python are pretty easy. For example, swapping numbers in Python is as
easy as writing (a, b)= (b, a).
It may also be stated here that learning something new is an involved and
intricate task. However, the simplicity of Python makes it almost a cake walk.
Moreover, learning advanced features in Python is a bit intricate, but is worth the
effort. It is also easy to understand a project written in Python. The code, in
Python, is concise and effective and therefore understandable and manageable.
Type and Run
In most projects, testing something new requires scores of changes and therefore
recompilations and re-runs. This makes testing of code a difficult and time
consuming task. In Python, a code can be run easily. As a matter of fact, we run
scripts in Python.
As we will see later in this chapter, Python also provides the user with an
interactive environment, in which one can run independent commands.
Syntax
The syntax of Python is easy; this makes the learning and understanding process
easy. According to most of authors, the three main features which make Python
attractive are that it’s simple, small, and flexible.
Mixing
If one is working on a big project, with perhaps a large team, it might be the case
that some of the team members are good in other programming languages. This

1.2.5
1.2.6
1.2.7
1.2.8
1.2.9
may lead to some of the modules in some other languages wanting to be
embedded with the core Python code. Python allows and even supports this.
Dynamic Typing
Python has its own way of managing memory associated with objects. When an
object is created in Python, memory is dynamically allocated to it. When the life
cycle of the object ends, the memory is taken back from it. This memory
management of Python makes the programs more efficient.
Built in Object Types
As we will see in the next chapter Python has built in object types. This makes
the task to be accomplished easy and manageable. Moreover, the issues related
to these objects are beautifully handled by the language.
Numerous Libraries and Tools
In Python, the task to be accomplished becomes easy—really easy. This is
because most of the common tasks (as a matter of fact, not so common tasks too)
have already been handled in Python. For example, Python has libraries which
help users to develop GUI’s, write mobile applications, incorporate security
features and even read MRI’s. As we will see in the following chapters, the
libraries and supporting tools make even the intricate tasks like pattern
recognition easy.
Portable
A program written in Python can run in almost every known platform, be it
Windows, Linux, or Mac. It may also be stated here that Python is written in C.
Free
Python is not propriety software. One can download Python compilers from
among the various available choices. Moreover, there are no known legal issues
involved in the distribution of the code developed in Python.

1.3
1.3.1
1.3.2
1.3.3
1.4
1.4.1
THE PARADIGMS
Procedural
In a procedural language, a program is actually a set of statements which execute
sequentially. The only option a program has, in terms of manageability, is
dividing the program into small modules. “C,” for example, is a procedural
language. Python supports procedural programming. The first section of this
book deals with procedural programming.
Object-Oriented
This type of language primarily focuses on the instance of a class. The instance
of a class is called an object. A class is a real or a virtual entity that has an
importance to the problem at hand, and has sharp physical boundaries. For
example in a program that deals with student management, “student” can be a
class. Its instances are made and the task at hand can be accomplished by
communicating via methods. Python is object-oriented. Section 2 of this book
deals with the object-oriented programming.
Functional
Python also supports functional programming. Moreover, Python supports
immutable data, tail optimization, etc. This must be music to the ears for those
from a functional programming background. Here it may be stated that
functional programming is beyond the scope of this book. However, some of the
above features would be discussed in the chapters that follow.
So Python is a procedural, object-oriented and functional language.
CHRONOLOGY AND USES
Having seen the features, let us now move onto the chronology and uses of
Python. This section briefly discusses the development and uses of Python and
will motivate the reader to bind with the language.
Chronology

1.4.2
Python is written in C. It was developed by Guido Van Rossum, who is now the
Benevolent Director for Life of Python. The reader is expected to take note of
the fact that Python has got nothing to do with pythons or snakes. The name of
the language comes from the show “Monty Python’s Flying Circus,” which was
one of the favorite shows of the developer, Guido van Rossum. Many people
attribute the fun part of the language to the inspiration.
Python is easy to learn as the core of the language is pretty concise. The
simplicity of Python can also be attributed to the desire of the developers to
make a language that was very simple, easy to learn but quite powerful.
The continuous betterment of the language has been possible because of a
dedicated group of people, committed to supporting the cause of providing the
world with an easy yet powerful language. The growth of the language has given
rise to the creation of many interest groups and forums for Python. A change in
the language can be brought about by what is generally referred to as the PEP
(Python Enhancement Project). The PSF (Python Software Foundation) takes
care of this.
Uses
Python is being used to accomplish many tasks, the most important of which are
as follows:
Graphical User Interface (GUI) development
Scripting web pages
Database programming
Prototyping
Gaming
Component based programming
If you are working in Unix or Linux, you don’t need to install Python. This is
because in Unix and Linux systems, Python is generally pre-installed. However,
if you work in Windows or Mac then you need to download Python. Once you
have decided to download Python, look for its latest version. The reader is
requested to ensure that the version he/she intends to download is not an alpha or
a beta version. Reference 1 at the end of the book gives a brief overview of
distinctions between two of the most famous versions. The next section briefly

1.5
discusses the steps for downloading Anaconda, an open source distribution
software.
Many development environments are available for Python. Some of them are as
follows:
1. PyDev with Eclipse
2. Emacs
3. Vim
4. TextMate
5. Gedit
6. Idle
7. PIDA (Linux)(VIM based)
8. NotePad++ (Windows)
9. BlueFish (Linux)
There are some more options available. However, this book uses IDLE and
Anaconda. The next section presents the steps involved in the installation of
Anaconda.
INSTALLATION OF ANACONDA
In order to install Anaconda, go to https://docs.continuum.io/anaconda/install
and select the installer (Windows or Mac OS or Linux). This section presents the
steps involved in the installation of Anaconda on the Windows Operating
System.
First of all, one must choose the installer (32 bit or 64 bit). In order to do so,
click on the selected installer and download the .exe file. The installer will ask
you to install it on the default location. You can provide a location that does not
contain any spaces or Unicode characters. It may happen that during the
installation you might have to disable your anti-virus software. Figures 1.2(a) to
1.2(g) take the reader through the steps of installation.

FIGURE 1.2(a) The welcome screen of the installer, which asks the user to close all running
applications and then click Next
FIGURE 1.2(b) The license agreement to install Anaconda3 4.3.0 (32 bit)

FIGURE 1.2(c) In the third step, the user is required to choose whether he wants to install
Anaconda for a single user or for all the users
FIGURE 1.2(d) The user then needs to select the folder in which it will install

FIGURE 1.2(e) The user then must decide whether he wants to add Anaconda to path
environment variable and whether to register Anaconda as the default Python 3.6
The installation then starts. After installation, the following screen will appear:
FIGURE 1.2(f) When the installation is complete, this screen appears

FIGURE 1.2(g) You can also share your notebooks on cloud
Once Anaconda is installed, you can open Anaconda and run your scripts. Figure
1.3 shows the Anaconda navigator. From the various options available you can
choose the appropriate option for you. For example, you can open the
QTConsole and run the commands/ scripts. Figure 1.4 shows the snapshot of
QTConsole. The commands written may appear gibberish at this point, but will
become clear in the chapters that follow.
FIGURE 1.3 The Anaconda navigator

1.6
FIGURE 1.4 The QtConsole
CONCLUSION
Before proceeding any further, the reader must take note of the fact that some
things in Python are different when compared to any other language. The
following points must be noted to avoid any confusion.
In Python, statements do not end with any special characters. Python
considers the newline character as an indication of the fact that the
statement has ended. If a statement is to span more than a single line, the
next line must be preceded with a ().
In Python, indentation is used to detect the presence of loops. The loops in
Python do not began or end with delimiters or keywords.
A file in Python is generally saved with a .py extension.
The shell can be used as a handy calculator.
The type of a variable need not to be mentioned in a program.
Choice at every step is good but can also be intimidating. As stated earlier,
Python’s core is small and therefore it is easy to learn. Moreover, there are some
things like (if/else), loops and exception handling which are used in almost all
the programs.

The chapter introduces Python and discusses the features of Python. One must
appreciate the fact that Python supports all three paradigms: procedural, object-
oriented, and functional. This chapter also paves the way for the topics presented
in the following chapters. It may also be stated that the codes presented in this
book will run on versions 3.X.
GLOSSARY
PEP: Python Enhancement Project
PSF: Python Software Foundation
POINTS TO REMEMBER
Python is a strong procedural, object-oriented, functional language crafted
in late 1980s by Guido Van Rossum.
Python is open source.
The applications of Python include software development, web
development, desktop GUI development, education and scientific
applications.
Python is popular due to its simplicity and robustness.
It is easy to interface with C++ and Java.
SciPy is used for engineering and mathematics, IPython for parallel
computing etc., Scions is used for build control.
The various development environments for Python are PyDev with Eclipse,
Emacs, Vim, TextMate, Gedit, Idle, PIDA (Linux)(VIM Based), NotePad++
(Windows), and BlueFish (Linux).
RESOURCES
To download Python, visit www.python.org
The documentation is available at www.python.org/doc/
EXERCISES

MULTIPLE CHOICE QUESTIONS
1. Python can subclass a class made in
(a) Python only
(b) Python, C++
(c) Python, C++, C#, Java
(d) None of the above
2. Who created Python?
(a) Monty Python
(b) Guido Van Rossum
(c) Dennis Richie
3. Monty Python was
(a) Creator of Python Programming Language
(b) British Comedy Group
(c) American Band
(d) Brother of Dosey Howser
4. In Python, libraries and tools
(a) Not supported
(b) Supported but not encouraged
(c) Supported and encouraged
(d) Supported (only that of PSF’s)
5. Python has
(a) Built in object types
(b) Data types
(c) Both

6. Python is a
(a) Procedural language
(b) object-oriented Language
(c) Fictional
(d) All of the above
7. There is no data type, so a code in Python is applicable to whole range of
Objects. This is called
(a) Dynamic Binding
(b) Dynamic Typing
(c) Dynamic Leadership
8. Which of the following is automatic memory management?
(a) Automatically assigning memory to objects
(b) Taking back the memory at the end of life cycle
(c) Both
9. PEP is
(a) Python Ending Procedure
(b) Python Enhancement proposal
(c) Python Endearment Project
(d) none of the above
10. PSF is
(a) Python Software Foundation
(b) Python Selection Function
(c) Python segregation function

11. What can be done in Python
(a) GUI
(b) Internet scripting
(c) Games
12. What can be done using Python?
(a) System programming
(b) Component based programming
(c) Scientific programming
13. Python is used in
(a) Google
(b) Raspberry Pi
(c) Bit Torrent
14. Python is used in
(a) App Engine
(b) YouTube sharing
(c) Real time programming
15. Which is faster?
(a) PyPy
(b) IDLE
(c) Both are equally good
(d) depends on the task

THEORY
1. Write the names of three projects which are using Python.
2. Explain a few applications of Python.
3. What type of language is Python? (Procedural, object-oriented or functional)
4. What is PEP?
5. What is PSF?
6. Who manages Python?
7. Is Python open source or proprietary?
8. What languages can be supported by Python?
9. Explain the chronology of the development of Python.
10. Name a few editors for Python.
11. What are the features of Python?
12. What is the advantage of using Python over other languages?
13. What is Dynamic Typing?
14. Does Python have data types?
15. How is Python different from Java?

Introduction to Python

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