Introduction-to-Python-print-datatype.pdf

Agenda
1
•History of python
2
•Features of python
3
•Basic syntax
2
Intro To Python

History of Python
• Python was developed by Guido van Rossum in the late eighties and early
nineties at the National Research Institute for Mathematics and Computer
Science in the Netherlands.
• Python is derived from many other languages, including ABC, Modula-3, C,
C++, Algol-68, SmallTalk, and Unix shell and other scripting languages.
• Python is copyrighted. Like Perl, Python source code is now available under
the GNU General Public License (GPL).
• Python is now maintained by a core development team at the institute,
although Guido van Rossum still holds a vital role in directing its progress.
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Intro To Python

Cons..
• Python is Interpreted − Python is processed at runtime by the interpreter.
You do not need to compile your program before executing it. This is similar to
PERL and PHP.
• Python is Interactive − You can actually sit at a Python prompt and
interact with the interpreter directly to write your programs.
• Python is Object-Oriented − Python supports Object-Oriented style or
technique of programming that encapsulates code within objects.
• Python is a Beginner's Language − Python is a great language for the
beginner-level programmers and supports the development of a wide range of
applications from simple text processing to WWW browsers to games.
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Intro To Python

Features of Python
• Easy-to-learn − Python has few keywords, simple structure, and a clearly
defined syntax. This allows the student to pick up the language quickly.
• Easy-to-read − Python code is more clearly defined and visible to the eyes.
• Easy-to-maintain − Python's source code is fairly easy-to-maintain.
• A broad standard library − Python's bulk of the library is very portable
and cross-platform compatible on UNIX, Windows, and Macintosh.
• Interactive Mode − Python has support for an interactive mode which
allows interactive testing and debugging of snippets of code.
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Intro To Python

Cons..
• Portable − Python can run on a wide variety of hardware platforms
and has the same interface on all platforms.
• Extendable − You can add low-level modules to the Python
interpreter. These modules enable programmers to add to or customize
their tools to be more efficient.
• Databases − Python provides interfaces to all major commercial
databases.
• GUI Programming − Python supports GUI applications that can be
created and ported to many system calls, libraries and windows
systems, such as Windows MFC, Macintosh, and the X Window system
of Unix
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Intro To Python

Amazing Projects Using Python
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Intro To Python

Battlefield 2
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Intro To Python

Basic Syntax
1. Variables Types
2. Basic Operators
3. Decision Making
4. Loops
5. Numbers
6. Strings
7. Lists
8. Function
9. Classes & Objects
10. Files I/O
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Intro To Python

Variable Types
• As in every language, a variable is the name of a memory location
• Python is weakly typed That is, you don’t declare variables to be a
specific type
• A variable has the type that corresponds to the value you assign to it
• Variable names begin with a letter or an underscore and can contain
letters, numbers, and underscores
• Python has reserved words that you can’t use as variable names
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Intro To Python

Python Reserved Words
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Intro To Python

Cons..
• At the >>> prompt, do the following:
x=5
type(x)
x=“this is text”
type(x)
x=5.0
type(x)
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Intro To Python

Input
• The following line of the program displays the prompt, the
statement saying “Press the enter key to exit”, and waits for
the user to take action
input("nnPress the enter key to exit.")
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Intro To Python

Printing
• You’ve already seen the print statement
• You can also print numbers with formatting
• These are identical to Java or C format specifiers
Print (“Hello World”)
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Intro To Python

Comments
• All code must contain comments that describe what it does
• In Python, lines beginning with a # sign are comment lines
➢You can also have comments on the same line as a statement
# This entire line is a comment
x=5 # Set up loop counter
• Multiple Line comment “”” Comments “””
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Intro To Python

Exercise
• Write a Python program which accepts
the radius of a circle from the user and
compute the area.
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Intro To Python

Day 2 ☺
Basic Operator
Intro To Python

Types of Operators
➢Arithmetic Operators
➢Relational Operators
➢Logical Operators
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Intro To Python

Arithmetic operators
➢Arithmetic operators we will use:
▪ + - * / addition, subtraction/negation, multiplication, division
▪ % modulus, a.k.a. remainder
▪ ** exponentiation
➢precedence: Order in which operations are computed.
▪ * / % ** have a higher precedence than + -
1 + 3 * 4 is
• Parentheses can be used to force a certain order of evaluation.
(1 + 3) * 4 is
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Intro To Python

Arithmetic operators
➢Arithmetic operators we will use:
▪ + - * / addition, subtraction/negation, multiplication, division
▪ % modulus, a.k.a. remainder
▪ ** exponentiation
➢precedence: Order in which operations are computed.
▪ * / % ** have a higher precedence than + -
1 + 3 * 4 is 13
➢Parentheses can be used to force a certain order of evaluation.
(1 + 3) * 4 is 16
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Intro To Python

Relational Operators
• Many logical expressions use relational operators:
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Intro To Python

Logical Operators
• These operators return true or false
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Intro To Python

Indentation
➢Python provides no braces to indicate blocks of code for
class and function definitions or flow control. Blocks of code
are denoted by line indentation, which is rigidly enforced.
➢The number of spaces in the indentation is variable, but
all statements within the block must be indented the same
amount.
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Intro To Python

Decision Making
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Intro To Python

The if Statement
• Syntax:
if <condition>:
<statements>
x = 5
if x > 4:
print(“x is greater than 4”)
print(“This is not in the scope of the if”)
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Intro To Python

The if Statement
• The colon is required for the if statement
• Note that all statement indented one level in from the if are within it scope:
x = 5
if x > 4:
print(“x is greater than 4”)
print(“This is also in the scope of the if”)
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Intro To Python

The if/else Statement
if <condition>:
<statements>
else:
<statements>
➢Note the colon following the else
➢This works exactly the way you would expect
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Intro To Python

Exercise
•Write a Python program to find whether
a given number (accept from the user) is
even or odd, print out an appropriate
message to the user.
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Intro To Python

Exercise
•Write a Python program to sum of three
given integers. However, if two values are
equal sum will be zero.
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Intro To Python

The for Loop
➢This is similar to what you’re used to from C or Java, but not the same Syntax:
for variableName in groupOfValues:
<statements>
➢Variable Name gives a name to each value, so you can refer to it in the statements.
➢Group Of Values can be a range of integers, specified with the range function.
➢Example:
for x in range(1, 6):
print (x, "squared is", x * x)
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Intro To Python

Range function
• The range function specifies a range of integers:
range(start, stop) - the integers between start (inclusive)
and stop (exclusive)
• It can also accept a third value specifying the change between values.
range(start, stop, step) - the integers between start (inclusive)
and stop (exclusive) by step
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Intro To Python

The while Loop
• Executes a group of statements as long as a condition is True.
• Good for indefinite loops (repeat an unknown number of times)
• Syntax:
while <condition>:
<statements>
• Example:
number = 1
while number < 200:
print (number)
number = number * 2
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Intro To Python

Exercise
•Write a Python program to compute
and display the first 16 numbers
powers of 2, starting with 1
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Intro To Python

Assignment 1
•Write a Python program to calculate
the sum of three given numbers, if the
values are equal then return thrice
of their sum.
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Intro To Python

Assignment 2
•Write a Python program to print all
even numbers from 1 to n using for
loop. Python program to generate all
even numbers between given range.
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Intro To Python

Day 3 ☺
Numbers & Strings
Intro To Python

Numbers
• Number data types store numeric values. They are immutable data
types, means that changing the value of a number data type results in
a newly allocated object.
• Number objects are created when you assign a value to them. For
example
var1 = 1
var2 = 10
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Intro To Python

Cons..
• Python supports four different numerical types −
• int (signed integers) − They are often called just integers or ints, are
positive or negative whole numbers with no decimal point.
• long (long integers ) − Also called longs, they are integers of unlimited size,
written like integers and followed by an uppercase or lowercase L.
• float (floating point real values) − Also called floats, they represent real
numbers and are written with a decimal point dividing the integer and
fractional parts. Floats may also be in scientific notation, with E or e
indicating the power of 10 (2.5e2 = 2.5 x 102 = 250).
• complex (complex numbers) − are of the form a + bJ, where a and b are
floats and J (or j) represents the square root of -1 (which is an imaginary
number). The real part of the number is a, and the imaginary part is b.
Complex numbers are not used much in Python programming.
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Intro To Python

Math Functions
• Use this at the top of your program: from math import *
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Intro To Python

Strings
• String: A sequence of text characters in a program.
• Strings start and end with quotation mark " or apostrophe ‘ characters.
• Examples:
"hello"
‘This is a string’
“This, too, is a string. It can be very long!”
• A string may not span across multiple lines or contain a " character.
"This is not
a legal String."
"This is not a "legal" String either."
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Intro To Python

Strings
• A string can represent characters by preceding them with a backslash.
• t tab character
• n new line character
• " quotation mark character
• backslash character
• Example: "HellottherenHow are you?"
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Intro To Python

Indexing Strings
➢As with other languages, you can use square brackets to index a string as if it were an
array:
name = “John Dove”
print(name, “starts with “, name[0])
• Output
John Dove starts with J
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Intro To Python

String Functions
• len(string) - number of characters in a string
• str.lower(string) - lowercase version of a string
• str.upper(string) - uppercase version of a string
• str.isalpha(string) - True if the string has only alpha chars
• Many others: split, replace, find, format, etc.
• Note the “dot” notation: These are static methods.
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Intro To Python

Exercise
•Write a Python program to compute
number of characters in a given string.
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Intro To Python

Exercise
•Write a Python program to get a string
and n (non-negative integer) copies of a
given string.
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Intro To Python

Exercise
•Write a Python program to test whether a
passed letter is a vowel or not.
•[aeiou]
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Intro To Python

Lists
• The most basic data structure in Python is the sequence. Each
element of a sequence is assigned a number - its position or index. The
first index is zero, the second index is one, and so forth.
• The list is a most versatile datatype 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.
➢list1 = ['physics', 'chemistry', 1997, 2000]
➢list2 = [1, 2, 3, 4, 5 ]
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Intro To Python

Lists
• To access values in lists, use the square brackets for slicing along with the index or
indices to obtain value available at that index. For example
• list1 = ['physics', 'chemistry', 1997, 2000]
• list2 = [1, 2, 3, 4, 5, 6, 7 ]
• print ("list1[0]: ", list1[0])
• print ("list2[1:5]: ", list2[1:5])
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Intro To Python

Lists
• You can update single or multiple elements of lists by giving the slice on the left-hand
side of the assignment operator, and you can add to elements in a list with the
append() method. For example
• list = ['physics', 'chemistry', 1997, 2000];
• print ("Value available at index 2 : “)
• print (list[2])
• list[2] = 2001;
• print "New value available at index 2 : "
• print (list[2])
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Intro To Python

Lists
• To remove a list element, you can use either the del statement if you know exactly
which element(s) you are deleting or the remove() method if you do not know. For
example
• list1 = ['physics', 'chemistry', 1997, 2000];
• print (list1)
• del (list1[2])
• print ("After deleting value at index 2 : “)
• print (list1)
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Intro To Python

Basic Lists Operation
Python Expression Results Description
len([1, 2, 3]) 3 Length
[1, 2, 3] + [4, 5, 6] [1, 2, 3, 4, 5, 6] Concatenation
['Hi!'] * 4 ['Hi!', 'Hi!', 'Hi!', 'Hi!'] Repetition
3 in [1, 2, 3] True Membership
for x in [1, 2, 3]: print x, 1 2 3 Iteration
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Intro To Python

Indexing, Slicing, and Matrixes
58
• L = ['spam', 'Spam', 'SPAM!’]
L[2] SPAM! Offsets start at zero
L[-2] Spam Negative: count from
the right
L[1:] ['Spam', 'SPAM!'] Slicing fetches sections
Intro To Python

Exercise
•Write a Python program to first print all
elements in a given list of integers then
sum of its element and print max value in
this list.
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Intro To Python

Exercise
•Write a Python program to create a
histogram from a given list of integers.
• Ex. [6,3,7]
• ******
• ***
• *******
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Intro To Python

Day 4 ☺
Tuples & Dictionary
Intro To Python

Tuples
➢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.
➢tup1 = ('physics', 'chemistry', 1997, 2000)
➢tup2 = (1, 2, 3, 4, 5 )
➢tup3 = "a", "b", "c", "d"
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Intro To Python

Tuples
➢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.
➢tup2 = (1, 2, 3, 4, 5 )
➢tup3 = "a", "b", "c", "d"
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Intro To Python

Accessing Values in Tuples
➢To access values in tuple, use the square brackets for slicing along
with the index or indices to obtain value available at that index.
➢tup2 = (1, 2, 3, 4, 5, 6, 7 )
➢print "tup1[0]: ", tup1[0]
➢print "tup2[1:5]: ", tup2[1:5]
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Intro To Python

Updating Tuples
➢Tuples are immutable which means you cannot update or change the
values of tuple elements. You are able to take portions of existing tuples
to create new tuples.
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Intro To Python

Delete Tuple Elements
➢Removing individual tuple elements is not possible. There is, of
course, nothing wrong with putting together another tuple with the
undesired elements discarded.
➢tup = ('physics', 'chemistry', 1997, 2000)
➢print (tup)
➢del tup;
➢print ("After deleting tup : “)
➢print (tup)
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Intro To Python

Basic Tuples Operations
len((1, 2, 3)) 3 Length
(1, 2, 3) + (4, 5, 6) (1, 2, 3, 4, 5, 6) Concatenation
('Hi!',) * 4 ('Hi!', 'Hi!', 'Hi!', 'Hi!') Repetition
3 in (1, 2, 3) True Membership
for x in (1, 2, 3): print x 1 2 3 Iteration
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Intro To Python

Indexing, Slicing, and Matrixes
68
• L = ('spam', 'Spam', 'SPAM!')
L[2] SPAM! Offsets start at zero
L[-2] Spam Negative: count from
the right
L[1:] ['Spam', 'SPAM!'] Slicing fetches sections
Intro To Python

Dictionaries
➢A dictionary is a data type similar to arrays, but works with keys and
values instead of indexes. Each value stored in a dictionary can be
accessed using a key, which is any type of object (a string, a number, a
list, etc.) instead of using its index to address it. Keys are unique
within a dictionary while values may not be. The values of a dictionary
can be of any type, but the keys must be of an immutable data type
such as strings, numbers, or tuples.
➢dict = {'Name': 'Zara', 'Age': 7, 'Class': 'First'}
➢print "dict['Name']: ", dict['Name']
➢print "dict['Age']: ", dict['Age']
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Intro To Python

Updating Dictionary
➢You can update a dictionary by adding a new entry or a key-value
pair, modifying an existing entry, or deleting an existing entry.
➢dict['Age'] = 8; # update existing entry
➢dict['School'] = "DPS School"; # Add new entry
➢print "dict['School']: ", dict['School']
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Intro To Python

Delete Dictionary Elements
➢You can either remove individual dictionary elements or clear the entire contents of
a dictionary. You can also delete entire dictionary in a single operation.
➢del dict['Name']; # remove entry with key 'Name'
➢dict.clear() # remove all entries in dict
➢del dict # delete entire dictionary
➢print "dict['School']: ", dict['School']
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Intro To Python

Properties of Dictionary Keys
➢Dictionary values have no restrictions. They can be any arbitrary
Python object, either standard objects or user-defined objects. However,
same is not true for the keys.
➢There are two important points to remember about dictionary keys :
➢(a) More than one entry per key not allowed. Which means no duplicate key is allowed.
When duplicate keys encountered during assignment, the last assignment wins.
➢ (b) Keys must be immutable. Which means you can use strings, numbers or tuples as
dictionary keys but something like ['key'] is not allowed
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Intro To Python

Exercise
➢Add "Jake" to the phonebook with the phone number 938273443, and
remove Jill from the phonebook.
➢phonebook = {"John" : 938477566, "Jack" : 938377264, "Jill" :
947662781}
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Intro To Python

Function
• A function is a block of organized, reusable code that is used to
perform a single, related action. Functions provide better modularity
for your application and a high degree of code reusing.
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Intro To Python

Function
• Define a function:
def <function name>(<parameter list>)
• The function body is indented one level:
def computeSquare(x):
return x * x
# Anything at this level is not part of the function
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Intro To Python

Exercise
➢Write a python program that calculates
power of number Ex- 6^5. Declare your
own function to do this.
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Intro To Python

Assign
➢Write a python program that simulate a
simple calculator to calculate basic
arithmetic operations.
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Intro To Python

Day 5 ☺
Classes and Objects
Intro To Python

Classes and Objects
➢Python has been an object-oriented language
since it existed. Because of this, creating and using
classes and objects are downright easy
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Intro To Python

OOP Terminology
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Intro To Python

Creating Classes
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Intro To Python
➢The class statement creates a new class definition. The
name of the class immediately follows the keyword class
followed by a colon
➢class ClassName:
'Optional class documentation string'
class_suite

Class Example
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Intro To Python
• class MyClass:
x = 5
• p1 = MyClass()
print(p1.x)

__init__() Function
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Intro To Python
➢All classes have a function called __init__(), which is always executed
when the class is being initiated.
➢Use the __init__() function to assign values to object properties, or
other operations that are necessary to do when the object is being
created
➢class Person:
def __init__(self, name, age):
self.name = name
self.age = age
p1 = Person("John", 36)
print(p1.name)
print(p1.age)

The self Parameter
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Intro To Python
➢The self parameter is a reference to the current instance of
the class, and is used to access variables that belongs to the
class.
➢It does not have to be named self , you can call it whatever
you like, but it has to be the first parameter of any
function in the class

Class Methods
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Intro To Python
• class Person:
• def __init__(self, name, age):
• self.name = name
• self.age = age
• def myfunc(self):
• print("Hello my name is " + self.name)
• p1 = Person("John", 36)
• p1.myfunc()

Destroying Objects
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• You have to define destructor
• def __del__(self):
print self.__class__.__name__, "destroyed"

Class Inheritance
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Intro To Python
• Instead of starting from scratch, you can create a class by deriving it
from a preexisting class by listing the parent class in parentheses
after the new class name.
• The child class inherits the attributes of its parent class, and you can
use those attributes as if they were defined in the child class. A child
class can also override data members and methods from the parent

Class Inheritance
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Intro To Python
• class SubClassName (ParentClass1[, ParentClass2,
...]):
'Optional class documentation string'
class_suite

Multiple Inheritance
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Intro To Python
• class A: # define your class A
• .....
• class B: # define your class B
• .....
• class C(A, B): # subclass of A and B
• .....

Data Hiding
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Intro To Python
• An object's attributes may or may not be visible outside the
class definition. You need to name attributes with a double
underscore prefix, and those attributes then are not be
directly visible to outsiders.

Overriding Methods
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Intro To Python
• You can always override your parent class methods. One reason for
overriding parent's methods is because you may want special or different
functionality in your subclass.
• class Parent: # define parent class
def myMethod(self):
print 'Calling parent method'
• class Child(Parent): # define child class
def myMethod(self):
print 'Calling child method'

Exercise
➢Create a base class, Telephone, and derive a
class ElectronicPhone from it. In Telephone,
create a string member phonetype, and a
function Ring() that outputs a text message
like this: "Ringing the <phonetype>."
In ElectronicPhone, the constructor should
set the phonetype to "Digital.“ then call
Ring() on the ElectronicPhone to test the
inheritance
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Intro To Python

Day 5 ☺
Files I/O
Intro To Python

Files I/O
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Intro To Python
• Python provides basic functions and methods necessary to
manipulate files by default. You can do most of the file
manipulation using a file object.

Opening and Closing Files
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Intro To Python
• Before you can read or write a file, you have to open it using
Python's built-in open() function. This function creates a file
object, which would be utilized to call other support methods
associated with it.
• file object = open(file_name [, access_mode][, buffering])

Modes of opening a file
96
Modes Description
r
Opens a file for reading only. The file pointer is placed at the beginning of the file. This
is the default mode.
rb
Opens a file for reading only in binary format. The file pointer is placed at the
beginning of the file. This is the default mode.
r+
Opens a file for both reading and writing. The file pointer placed at the beginning of
the file.
rb+
Opens a file for both reading and writing in binary format. The file pointer placed at
the beginning of the file.
w
Opens a file for writing only. Overwrites the file if the file exists. If the file does not
exist, creates a new file for writing.
wb
Opens a file for writing only in binary format. Overwrites the file if the file exists. If
the file does not exist, creates a new file for writing
Intro To Python

97
Modes Description
w+
Opens a file for both writing and reading. Overwrites the existing file if the file exists.
If the file does not exist, creates a new file for reading and writing
wb+
Opens a file for both writing and reading in binary format. Overwrites the existing file
if the file exists. If the file does not exist, creates a new file for reading and writing
a
Opens a file for appending. The file pointer is at the end of the file if the file exists.
That is, the file is in the append mode. If the file does not exist, it creates a new file for
writing
ab
Opens a file for appending in binary format. The file pointer is at the end of the file if
the file exists. That is, the file is in the append mode. If the file does not exist, it
creates a new file for writing
a+
Opens a file for both appending and reading. The file pointer is at the end of the file if
the file exists. The file opens in the append mode. If the file does not exist, it creates a
new file for reading and writing
ab+
Opens a file for both appending and reading in binary format. The file pointer is at the
end of the file if the file exists. The file opens in the append mode. If the file does not
exist, it creates a new file for reading and writing
Intro To Python

The close() Method
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Intro To Python
• The close() method of a file object flushes any unwritten
information and closes the file object, after which no more
writing can be done.
• Python automatically closes a file when the reference object
of a file is reassigned to another file. It is a good practice to
use the close() method to close a file.
• fileObject.close()

Reading and Writing Files
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Intro To Python
• The file object provides a set of access methods to make our
lives easier. We would see how to use read() and write()
methods to read and write files.

The write() Method
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Intro To Python
• The write() method writes any string to an open file. It is
important to note that Python strings can have binary data
and not just text.
• The write() method does not add a newline character ('n')
to the end of the string.
• fo = open("foo.txt", "w")
• fo.write( "Python is a great language.nYeah its great!!n")

The read() Method
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Intro To Python
• The read() method reads a string from an open file. It is
important to note that Python strings can have binary data.
apart from text data.
• f = open("demofile.txt", "r")
• print(f.read(5))

The read() Method
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Intro To Python
• print(f.read())
• print(f.readline())
• for x in f:
• print(x)

File Remove
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• import os
• os.remove("demofile.txt")

File Positions
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Intro To Python
• The tell() method tells you the current position within the file; in other
words, the next read or write will occur at that many bytes from the
beginning of the file.
• The seek(offset[, from]) method changes the current file position. The
offset argument indicates the number of bytes to be moved. The from
argument specifies the reference position from where the bytes are to
be moved.
• If from is set to 0, it means use the beginning of the file as the
reference position and 1 means use the current position as the
reference position and if it is set to 2 then the end of the file would be
taken as the reference position.

Exercise
➢Write a python program that computes
the size of file called “student.txt” which
has the following statements.
➢My name is ali
➢I am 20 years old
105
Intro To Python

Useful Links
106
Intro To Python
• https://docs.python.org/3/
• https://www.udacity.com/course/introduction-to-python--
ud1110
• https://www.geeksforgeeks.org/python-programming-
language/

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