Introduction python

K M Kiran
jumbotechnos@gmail.com

Agenda
What is Python…?
Differences between program and scripting language
History of Python
Scope of Python
Why do people use Python?
Installing Python IDE
Who uses python today
What can I do with python
A Sample Code
Python code execution
Running Python

What is Python…?
Python is a general purpose programming language that is
often applied in scripting roles.
So, Python is programming language as well as scripting
language.
Python is also called as Interpreted language

Differences between program and
scripting language
Program
a program is executed (i.e.
the source is first compiled,
and the result of that
compilation is expected)
A "program" in general, is a
sequence of instructions
written so that a computer
can perform certain task.
Scripting
a script is interpreted
A "script" is code written in
a scripting language. A
scripting language is nothing
but a type of programming
language in which we can
write code to control
another software application.

History
Invented in the Netherlands, early 90s by Guido van Rossum
Python was conceived in the late 1980s and its
implementation was started in December 1989
Guido Van Rossum is fan of ‘Monty Python’s Flying
Circus’, this is a famous TV show in Netherlands
Named after Monty Python
Open sourced from the beginning

Python’s Benevolent Dictator For Life
“Python is an experiment in how much
freedom program-mers need. Too
much freedom and nobody can read
another's code; too little and
expressive-ness is endangered.”
- Guido van Rossum

Why was python created?
"My original motivation for creating Python was the
perceived need for a higher level language in the
Amoeba [Operating Systems] project.
I realized that the development of system
Moreover, doing these things in the Bourne
administration utilities in C was taking too long.
shell
wouldn't work for a variety of reasons. ...
So, there was a need for a language that
would bridge the gap between C and the shell”
- Guido VanRossum

Scope of Python
Science
- Bioinformatics
SystemAdministration
-Unix
-Web logic
-Web sphere
WebApplication Development
-CGI
-Jython – Servlets
Testing scripts

Why do people use Python…?
The following primary factors cited by Python users
seem to be these:
Python is object-oriented
Structure supports such concepts as polymorphism, operation
overloading, and multiple inheritance.
Indentation
Indentation is one of the greatest future in Python.
It's free (open source)
Downloading and installing Python is free and easy
Source code is easily accessible

It's powerful
- Dynamic typing
- Built-in types and tools
- Library utilities
- Third party utilities (e.g. Numeric, NumPy, SciPy)
-Automatic memory management
It's portable
- Python runs virtually every major platform used today
-As long as you have a compatible Python interpreter installed,
Python programs will run in exactly the same manner,
irrespective of platform.

It's mixable
- Python can be linked to components written in other languages easily
- Linking to fast, compiled code is useful to computationally intensive
problems
- - Python/C integration is quite common
It's easy to use
- No intermediate compile and link steps as in C/ C++
- Python programs are compiled automatically to an intermediate
form called bytecode, which the interpreter then reads
- This gives Python the development speed of an interpreter without
the performance loss inherent in purely interpreted languages
It's easy to learn
- Structure and syntax are pretty intuitive and easy to grasp

Installing Python
Python is pre-installed on most Unix systems, including
Linux and MAC OSX
But for in Windows Operating Systems , user can
download from the https://www.python.org/downloads/
- from the above link download latest version of python
IDE and install, recent version is 3.4.1 but most of
them uses version 2.7.7 only

After installing the
Python Ver#2.7.7, go to
start menu then click on
python 2.7 in that one
you can select python
(command line) it is
prompt with >>>

Who uses python today…
Python is being applied in real revenue-generating products
by real companies. For instance:
Google makes extensive use of Python in its web search
system, and employs Python’s creator.
Intel, Cisco, Hewlett-Packard, Seagate, Qualcomm, and IBM
use Python for hardware testing.
ESRI uses Python as an end-user customization tool for its
popular GIS mapping products.
The YouTube video sharing service is largely written in
Python

What can I do with Python…?
System programming
Graphical User Interface Programming
Internet Scripting
Component Integration
Database Programming
Gaming, Images, XML , Robot and more

A Sample Code
# A comment.
# Another one.
x = 34 - 23
y = “Hello”
z = 3.45
if z == 3.45 or y == “Hello”:
x = x + 1
# String concat.y = y + “ World”
print x
print y

Enough to understand the code
Indentation matters to code meaning
-Block structure indicated by indentation
First assignment to a variable creates it
- Variable types don’t need to be declared.
-Python figures out the variable types on its own.
Assignment is = and comparison is ==
For numbers + - * / % are as expected
- Special use of + for string concatenation and % for string
formatting (as in C’s printf)
Logical operators are words (and, or, not) not symbols
The basic printing command is print

Python Code Execution
Python’s traditional runtime execution model: source code you
type is translated to byte code, which is then run by the Python
Virtual Machine. Your code is automatically compiled, but then
it is interpreted.
Source code extension is .py
Byte code extension is .pyc (compiled python code)

Running Python
Once you're inside the Python interpreter, type in commands at will.
• Examples:
>>> print 'Hello world'
Hello world
# Relevant output is displayed on subsequent lines without the >>>
symbol
>>> x = [0,1,2]
# Quantities stored in memory are not displayed by default
>>> x
# If a quantity is stored in memory, typing its name will display it
[0,1,2]
>>> 2+3
5

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