Ilucbe python v1.2

Programming is Fun
An introduction to Python

Indian Linux Users Group Coimbatore
http://ilugcbe.org.in
mail2ilugcbe@gmail.com

ILUG-CBE Programming is Fun

Our Inspiration

Kenneth Gonsalves (1953-2012)


About


Purpose

Learn art of computer programming with one of the easiest
programming language in the world.
Get ready to enjoy the joy of programming in Python.


Warning

This is a hands on training program.
No theory included in the slides; it may discussed whenever
and wherever it is required.
Be patient,listen, practice and ask questions
Do not hesitate to experiment
Our volunteers are here to help you in practising
Be courageous enough to try
We are leaning Python not rocket science
Be simple and think in a simplistic way

Are You Ready !


Why Python

Why
Used almost everywhere
Fun
Concise
Simple
Powerful
Filled with spices to write eﬀective programs


Installation

Already installed in GNU/Linux systems
If you are using M$ Windows download Python from python.org
If you are downloading Python for Windows remember to
download Python 2.7 only.


Interactive Interpreter


Interpreter

Contains REPL
Read
Evaluate
Print
Loop


Interpreter


Hello World!!

Why Hello World
Writing ’Hello World’ program is the ritual to please the
programming gods to be a good programmer!!

>>> print "Hello World"
Hello world


Let’s Jump to Programming


Programming Practice - 1

Create a ﬁle hello.py
type print ”Hello World”
Listen to the screen for instructions.
In-case of any issues just raise your hand our volunteers will be
there to help you.


Programming Practice - 1

Run the program

$python hello.py


Time to make your hands dirty

Note
Make sure that you have understood the ﬁrst step.
In-case of trouble we can practice it for couple of minutes.


Variables

age = 33 # Integer
avg = 33.35 # Float
name = "linux" # String
bool = True # Boolean
another = "44" # String


Variables - naming

use lowercase
use underscore between words my age
do not start with numbers
do not use built-ins
do not use keywords


Reserved

and del for is raise assert elif from lambda return break else global
not try class except if or while continue exec import pass yield def
ﬁnally in print


Time to make your hands dirty


Everything is an object
Everything in python is an object
An object has
identity (id)
type (type)
value (mutable or immutable)

>>> age = 33
>>> type(age)
<type ’int’>
>>> id(age)
167263248
>>> age 34
>>> id(age)
167263236


Casting

>>> age = 33
>>> str(age)
’33’
>>> float(age)
33.0
>>> long(age)
33L
>>> int(age)
33


Time for some maths

+ , - , * , ** (power),% (modulo), // (ﬂoor division), < (less than)
> greater than, <=, >=, ==


It is maths time now


String

>>> name = ’linux’
>>> address = "Coimbatore 1st street"
>>> description = """ We are teaching python to
young chaps"""
>>> with_new = "this sentence have one n new line"


String

>>> name = "linux"
>>> nameu = name.upper()
>>> namel = nameu.lower()
>>> namel.find(’l’)
>>> ",".join(name)
>>> name.startswith(’l’)
>>> name.endswith(’x’)
>>> namet = name.title()
>>> wspace = " with space "
>>> stripped = wspace.strip()


Playing with String


Comments

Single line comments starts with #
Multi-line comments should be with in ””” ”””

>>> avg = 45.34 #float
>>> name = "ilug-cbe" """ This is a
multiline comment """


Boolean

>>> t = True
>>> f = Flase

>>> n = None


Conditionals

equality,greater,less,is, is not ...
==, ! =, >, >=, <, <=, is, is not


Conditionals

>>> 1 == 1
>>> 1 >= 0
>>> 0 <= 1
>>> 0 != 1
>>> "Rajani" is "rajani"
>>> "Vijay" is not "Rajani"
>>> name = None
>>> if name is not None:
... #do something


Boolean operators

Used to combine conditional logic
and
or
not


if ...

if mark > 60 and mark < 100:
print "First Class"
elif mark < 60:
print "Second Class Only :-("
else:
print "Ooops !!!!"


if ... elif time


Sequences

list
List is an ordered collection of objects.

names = ["rms","linus","guido","larry"]
marks = [45,50,60,80,90]
mixed = ["linux",12,12.35,90L]


Sequences - list

names = []
print names
names.append("linus")
print names
numbers = [6,9,2,3,1,8,4]
print len(numbers)
print numbers.sort()
print numbers.reverse()
another = [9,3,6]
numbers.extend(another)
print numbers
numbers.insert(0,20)
print numbers


Sequences - list

print numbers[0]
print numbers[-1]
print numbers[2:-2]
print numbers[:-2]
print numbers[2:]
print numbers[:]


Sequences -tuple

tuple
Tuple is like list only. But tuple is immutable

nums = (1,2,3,4)
print nums
print len(nums)
print nums[0]
print nums[-1]


Sequences range

nums = range(20)
print nums
selected = range(20,60)
print selected
jump2 = range(10,100,2)
print jump2


Let’s do some sequencing


Iteration

names = ["linus","rms","guido","larry"]
for name in names:
print "hello %s" %(name)

for num in range(10,20,2):
print num


Iteration

for i in range(len(names)):
print i,names[i]

for i,v in enumerate(names):
print i,v


Iteration break,continue and pass

for name in names:
print name
if name == "guido":
break

for name in names:
print name
if name == "linus":
continue

for name in names:
print name
if name == "rms":
pass


Iteration - while

my_number = 10

while my_number < 20:
print my_number
my_number += 2


Let’s Iterate


Dictionaries

Also called as hash, hashmap or associative array

address = {"name":"ILUG-CBE","houseno":"Nil",
"street":"any whare","city":"Coimbatore"}
print address


Dictionaries

address["state"] = "tamilnadu"
address["web"] = "ilugcbe.org.in"

print address


Dictionaries

print address.has_key("country")

print address.get("phone","No Phone Number Provided")


Dictionaries

address.setdefault("country","India")

print address

print address.keys()

print address.values()

print address.items()

del address["country"]

print address


Let’s practice Dictionaries


Functions

def say_hai():
print "hello"

say_hai()


Functions

def add_two(num):
return num + 2

res = add_two(4)

print res


Functions

def add(a,b):
"""
adds two numbers
"""
return a + b

res = add_two(4,5)

print res


Functions

def demo(*args):
"""
*args demo
"""
for arg in args:
print i * 2

demo(1,2,3,4,5,6)


Functions

def demo(num,*args):
"""
*args demo
"""
for arg in args:
print i * num

demo(1,2,3,4,5,6)


Functions

def demo(num,*args):
"""
*args demo
"""
mul = []
for arg in args:
mul.append(i * num)

return sum(mul)

res = demo(2,2,3,4,5,6)

print res


Functions

def marker(roll_no,details):
if details[’marks’] > 60:
print "Roll no %d %s" %(roll_no, "First Class")

marker(12,marks = 62)


Functions

def mulbythree(num,three=3):
"""
default argument example
"""
return num * three

res = mulbythree(43)
print res


Be functional now


Tricks 1

nums = [1,2,3,4,5,6,7,8,9]
mulbt = [num * 2 for num in nums]

print nums
print mulbt


Tricks - 2

nums = [1,2,3,4,5,6,7,8,9]
mulbt = [num * 2 for num in nums if num / 2 != 0]

print nums
print mulbt


Tricks - 3

nums = [1,2,3,4,5,6,7,8,9]
numtuple = tuple(nums)

print type(nums)
print type(numtuple)


Tricks - 4

print "ILUGCBE".lower().upper().title()


User input

name = raw_input("Tell your name: ")

print name

age = int(raw_input("Tell your age: "))

print age


Tricks time


Lambda

product = lambda x,y : x * y

res = product(12,13)
print res


Lambda

dbtnt = lambda x : x * 2 if x % 2 == 0 else x

res = dbtnt(12)
print res


Lambda

bors = lambda x: x > 100 and ’big’ or ’small’

for i in (1, 10, 99, 100, 101, 110):
print i, ’is’, f(i)


Object Oriented Programming - basics

class MyClass:
"""
This is my class
"""
def __init__(self):
#nothing

def say_hai(self):
print "Hai"

obj = MyClass()
obj.say_hai()



class MyClass(object):
"""
This is my class
"""
def __init__(self):
#nothing

def say_hai(self):
print "Hai"

obj = MyClass()
obj.say_hai()



class Student:
"""
Student class
"""

def __init__(self):
self.college = "My College"

def greet(self,name):
"""
Function to greet student
"""
print "Hello %s from %s" %(name, self.college)

student = Student()
student.greet("Jaganadh")

Object Oriented Programming - inheritance

class BeStudent:
def __init__(self):
Student.__init__(self)
self.class = "BE First Year"

def greet(self,name):
print "Hello %s from %s %s class" %(name,
self.college,self.class)

student = BeStudent()
student.greet("Jaganadh G")


Object Oriented Time


File I/O - read ﬁle

input = open("file.txt",’r’)
contents = input.read()
input.close()

print contents

input = open("file.txt",’r’)
contents = input.readlines()
input.close()

print contents


File I/O - write to ﬁle

names = ["linus","rms","larry","guido"]
output = open("out_file.txt",’w’)
for name in names:
output.write(name)
output.write("n")


File I/O - write to ﬁle

names = ["linus","rms","larry","guido"]
output = open("out_file.txt",’a’)
for name in names:
output.write(name)
output.write("n")


Let’s play with ﬁles


Batteries

Standard Libraries
Python comes with batteries included. Lots of useful libraries are
there in the language. Let’s see some of these libraries now

import math
print math.pi
print math.sqrt(10)
print math.factorial(10)
print math.sin(10)
print math.pow(10,2)
print math.log(10)
print math.log(10,2)
print math.log10(10)
print math.exp(10)


Batteries - sys

import sys
print sys.platform

afl = sys.argv[1]

print sys.version
print sys.maxint
print sys.maxsize


Batteries - os

import os
print os.curdir()
print os.getlogin()
print os.getcwd()
print os.name


Batteries - time,random

import time
print time.ctime()
print time.gmtime()

import random
print random.random()
print random.choice([1,2,3,4,5,6])


Battery Recharge


Question Time


Contributors

Jaganadh G @jaganadhg
Biju B @bijubk
Satheesh Kumar D
Sreejith S @tweet2sree
Rajith Ravi @chelakkandupoda


Contact US

Web
http://ilugcbe.org.in
mail mail2ilugcbe@gmail.com


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