Python-The programming Language

What is Python?
 High- level language.
 Object oriented
 Interpreted
 Server scripting language.

Designed by Guido Van
Rossum in 1989.
Developer

Why Python?
 Designed to be easy to learn and master.
- Clean and clear syntax
- Very few keywords
 Highly portable.
-Runs almost everywhere
 Extensible.
 Reduced development Time
-code is 2-10x shorter than C,C++ and Java.

Who uses
Python?
 Google
 Yahoo
 NASA
 PBS
 ….the list goes on

Applications
 Software Development
 Web developments and its applications
 Mobile applications
 Embedded devices
 Networking programming

Python Interpreter
$gedit file.py (mainly used in linux)
$ python file.py
or
$python

Variables
Syntax: variable_name = value
>>> answer = 42
>>> PI = 3.14
>>> team = ‘B25’
>>> truthy = True
>>> falsey = False
>>> nil = None
>>> choice = ‘a’

Data Types
>>> type(1)
<type ‘int’>
>>> type(PI)
<type ‘float’>
>>> type(team)
<type ‘str’>
>>> type(truthy)
<type ‘bool’>
>>> type(falsey)
<type ‘bool’>
>>> type(nil)
<type ‘NoneType’>
Note: ’type’ keyword return the
type of data it receives as
argument.

Comments
Single Line Comment Multiple Line Comment
# I Love Python
# Python uses interpreter
""" It is easy to initialize a
variable using python"""

Indentation
IndentationError: expected an
indented block
Compiles
def spam(a):
pizza = pizza + a
return pizza
print spam(5)
def spam(a):
pizza = pizza + a
return pizza
print spam(5)

Arithmetic and logical
operators

Addition
>>> print 6+1
7
Substraction
>>>print 6-2
4
Multiplication
>>>print 3*2
6
Division
>>>print 10/2
5

Exponentiation
(**)
>>> print 2 ** 10
1024
>>> print 3.0**2
9.0
Modulo(%)
>>>print 3%2
1
>>>print 5%3
2

Strings
>>>hi=“Hello World”
>>>print hi
Hello World
>>>sem=“Hangman”
Indexing In Strings
>>> hi='hello Jarvis'
>>> print hi[-1]
s

String Concatenation
String concatenation is a process in which two strings are merged together.
’+’ operator is used for concatenation.
Example:
>>>message=“Hello”
>>>messageone=“Jharvard”
>>>print message + messageone
HelloJharvard
>>>h=“python”
>>> a=2
>>>print h +str(a)
python2

>>>var = 100
>>>if var == 200:
print “PLUTO"
print var
>>>elif var == 100:
print "DONALD"
print var
>>>else:
print "DAISY"
print var
OUTPUT:
DONALD
100
Example:

Loops
For……
for <item> in <collection>: #Syntax
<body>
>>>for letter in 'Python': # First Example
print 'Current Letter :', letter
Current Letter : P
Current Letter : y
Current Letter : t
Current Letter : h
Current Letter : o
Current Letter : n

While………
>>>def factorial(n):
num = 1
while n >= 1:
num = num * n
n = n - 1
return num
>>>fact(5)
120

Functions
Function Syntax:
The Python interpreter has a number of functions built into it that are
available. But if the user want to define his own function he must
def factorial(arg):
num=1
while(arg>=1):
num=arg*num
arg=arg-1
return num
Example:
>>>factorial(5)
120

Data Structures
Data Structures in python usually consist of Compound Data
types.. These data types are of three categorizes:
1.Tuples
2.Lists
3.Dictionaries

Tuples
A tuple is an immutable sequence of elements.
Created with ().
>>>a=(1,8,5,4,6)
>>>print a
(1,8,5,4,6)
For Singleton Tuple we use :
>>>a=(1,)
>>>print a
(1)
>>>del tuplename #delete the tuple

Lists
• Look a lot like tuples
– Ordered sequence of values, each identified by an index
– Use [1,2,3] rather than (1,2, 3)
– Singletons are now just [4] rather than (4, )
• BIG DIFFERENCE
– Lists are mutable!!
– While tuple, int, float, str are immutable
– So lists can be modified after they are created!

len(list)
max(list)
min(list)
list.append(obj)
list.count(obj)
list.index(obj)
list.reverse()
list.remove(obj)
list.insert(i,obj)
list.pop([i])
list.sort()
List Methods:

Example:
>>>lst=[5,8,3,4,6,4]
>>>print len(lst)
>>>print max(lst)
>>>print min(lst)
>>>lst.append(10)
>>>print lst
>>>print lst.count(4)
>>>lst.reverse()
>>>print lst
>>>lst.remove(6)
>>>print lst
>>>lst.insert(1,0)
>>>print lst
>>>print lst.pop(3)
>>>lst.sort()
>>>print lst
Output:
6
8
3
[5, 8, 3, 4, 6, 4, 10]
2
[10, 4, 6, 4, 3, 8, 5]
[10, 4, 4, 3, 8, 5]
[10, 0, 4, 4, 3, 8, 5]
4
[0, 3, 4, 5, 8, 10]

Dictionary
Dictionary is an unordered set of key:value pairs.
Key are always unique to values.
Use {} curly brackets to construct the dictionary,and [] square
brackets to index it.
d = {'key1' : 1, 'key2' : 2, 'key3' : 3}
Monthly_numbers={‘Jan’:1, ’Feb’:2, ’Mar’:3,
1 :’Jan’, 2 :’Feb’,3 :’Mar’}
>>>Monthly_numbers[‘Feb’]
2
Syntax:

Dictionary methods
● clear()
● copy()
● has_key()
● keys()
● pop()
● values()
● del dict_name[key_name]
● dict_nme[key_name]=value

What do you mean by Range()
in python?

In python range () is a function that is used as a
shortcut for generating list.
It is of 3 different types:
1.range(start,stop)
2.range(stop)
3.range(start ,stop,step)
Examples:
>>>range(5,10)
[5,6,7,8,9] #last element will not be included
>>>range(5,10,2)
[5,7,9]
>>>range(5)
[0,1,2,3,4]

Importing Modules
 import <module_name>
 from <module_name> import <module>
 from <module_name> import *
A module is a python file that (generally) has only definitions of
variables, functions, and classes.

Example:
>> import math
>>> print math.sqrt(25)
5
>>> from math import *
>>> sqrt(36)
6
>>>pi
3.145926535897931
>>>from datetime import datetime
>>>now=datetime.now()
>>>now.year
2015
>>>now.month
7
>>>now.day
21

Python-The programming Language

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