Python Introduction

PYTHON
Presented by:
R. Punithavel

What We Give you?
2
• What is Python…?
• Differences between program and scripting language
• History of Python
• Scope of Python
• What can I do with python
• Who uses python today
• Why do people use Python?
• Installing Python IDE
• ASample Code
• Python code execution
• Running Python
• Python Basic(Variable, Strings, Data types etc.)

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
3

Differences between program and
scripting language
4
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
5
• 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 V
an 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 programmers need.
Too much freedom and nobody can
read another's code; too little and
expressiveness is endangered.”
- Guido van Rossum
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Why was python created?
7
"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
administration utilities in C was taking too
in the Bourne
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 Van Rossum

Scope of Python
8
• Science
- Bioinformatics
• SystemAdministration
-Unix
-Web logic
-Web sphere
• Web Application Development
-CGI
-Jython – Servlets
• Testing scripts

What can I do with Python…?
9
• System programming
• Graphical User Interface Programming
• Internet Scripting
• Component Integration
• Database Programming
• Gaming, Images, XML , Robot and more

Who uses python today…
10
• 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 Y
ouTube video sharing service is largely written in
Python

Why do people use Python…?
11
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.
.
• 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.
12

Installing Python
13
• Python is pre-installed on most Unix systems, including Linux
and MAC OS X
• 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 >>>
14

Running Python
16
Once you're inside the Python interpreter, type in commands at will.
• Examples:
>>> print 'Hello world'
Hello world

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)
17

Math
Try typing this into Code:
>>> print 3 + 12
15
>>> print 12 – 3
9
>>> print 9 + 5 – 15 + 12
11
Operators:
add: +
subtract: -
Note: don’t type the arrows >>> !
19

Math
Rule: If you want Python to answer in floats, you have to
talk to it in floats.
More operators:
divide: /
multiply: *
>>> print 3 * 12
>>> print 12 / 3
>>> print 11 / 3
>>> print 12.0 / 3.0
>>> print 11.0 / 3.0
36
4
3
4.0
3.66
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Math
21
Practice:
>>> print 2 < 3 True
>>> print 2 <= 2 False
>>> print 3 > 2 True
>>> print 2 != 3 True
>>> print False < True True

Strings
23
Examples:
Try typing one without quotes:
What’s the result?
>>> “It’s a beautiful
day!”
>>> “Goodbye, cruel
world.”
>>> Aggies
>>> “Aggies”
>>> “Rice fight, never
die!”
>>> “3 + 2”

Strings
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String operators:
concatenation: +
multiplication: *
Try concatenating:
Try multiplying:
>>>
“ “
print “Hello”
+ “world!”
+
>>>
250
print “HAHA” *

Variable
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Create a Variable:
>>>headmaster=“Dumbledore”
>>>print headmaster
‘Dumbledore’
Assigning a New Value:
>>>headmaster=“Hardcastle”
>>>print headmaster
‘Hardcastle’

Data Type:
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Python has many native data types. Here are the important ones:
Booleans are either True or False.
Numbers can be integers (1 and 2), floats (1.1 and 1.2), fractions
(1/2 and 2/3), or even complex numbers.
Strings are sequences of Unicode characters, e.g. an HTML
document.
Bytes and byte arrays, e.g. a JPEG image file.
Lists are ordered sequences of values.
Tuples are ordered, immutable sequences of values.
Sets are unordered bags of values.

Example:
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String
Integer
Float
List
“Whoop!”
42
3.14159
[“John”, “Paul”, “George”, “Ringo”]
Python can tell us about types using the type()
function:
>>> print type(“Whoop!”)
<type ‘str’>

List:
31
The list is a most versatile Data type available in Python
which can be written as a list of comma-separated values
(items) between square brackets. Important thing about a
list is that items in a list need not be of the same type.
Example:
list1 = ['physics', 'chemistry', 1997, 2000];
list2 = [1, 2, 3, 4, 5 ];

SN Function with Description
1 cmp(list1, list2) Compares elements of both lists.
2 len(list) Gives the total length of the list.
3 max(list) Returns item from the list with max value.
4 min(list) Returns item from the list with min value.
5 list(seq) Converts a tuple into list.
32

List: a sequence of objects
33
>>> Beatles = [“John”, “Paul”, “George”,
“Ringo”]
>>> grades = [82, 93, 67, 99, 100]
Guess what this will output:
>>> type(Beatles)
>>> type(grades)

Lists
Index: Where an item is in the list
34
>>> Beatles = [“John”, “Paul”, “George”,
“Ringo”]
>>> Beatles[0]
‘John‘
[“John”, “Paul”, “George”, “Ringo”]
0 1 2 3
Python always starts at zero!

Tuples:
36
A tuple is a sequence of immutable Python objects. Tuples are
sequences, just like lists. The differences between tuples and
lists are, the tuples cannot be changed unlike lists and tuples
use parentheses, whereas lists use square brackets.
Example:
tup2 = (1, 2, 3, 4, 5 );
tup3 = ("a", "b", "c", "d“);
Accessing Values:
print "tup2[1:5]: “
Output:
tup2[1:5]: [2, 3, 4, 5]

Built-in Tuple Functions
37
Python includes the following tuple functions −
SN Function with Description
1 cmp(tuple1, tuple2) Compares elements of both tuples.
2 len(tuple) Gives the total length of the tuple.
3 max(tuple) Returns item from the tuple with max value.
4 min(tuple) Returns item from the tuple with min value.
5 tuple(seq) Converts a list into tuple.

LOOPS & CONDITIONAL
STATEMENTS
38

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Loop Type Description
while loop Repeats a statement or group of statements
while a given condition is TRUE. It tests the
condition before executing the loop body.
for loop Executes a sequence of statements multiple
times and abbreviates the code that
manages the loop variable.
nested loops You can use one or more loop inside any
another while, for or do..while loop.

Statement Description
if statements An if statement consists of a boolean expression
followed by one or more statements.
if...else statements An if statement can be followed by an
optional else statement, which executes when
the boolean expression is FALSE.
nested if statements You can use one if or else if statement inside
another if or else if statement(s).
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I believe the trial has shown conclusively that it is both possible and
desirable to use Python as the principal teaching language:
o It is Free (as in both cost and source code).
o It is trivial to install on a Windows PC allowing students to take
their interest further. For many the hurdle of installing a Pascal or
C compiler on a Windows machine is either too expensive or too
complicated;
o It is a flexible tool that allows both the teaching of traditional
procedural programming and modern OOP; It can be used to
teach a large number of transferable skills;
o It is a real-world programming language that can be and is used in
academia and the commercial world;
o It appears to be quicker to learn and, in combination with its many
libraries, this offers the possibility of more rapid student
development allowing the course to be made more challenging
and varied;
o and most importantly, its clean syntax offers increased
understanding and enjoyment for students;
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