introduction to python

Introduction to
Python
Jincy M Nelson

PYTHON
• A programming language developed
by Guido Van Rossum in feb-1991.
• Named after a comedy show namely
‘Monty Python’s Flying Circus’.
• It is based on ABC language.
• It is an open source language.

Features of Python
 It is an pen source, so it can be
modified and redistributed.
 Uses a few keywords and clear
,simply English like structure.
 Can run on variety of platforms.
 Support procedure oriented as well as
object oriented programming.

Features of Python
 It support Graphical user interface.
 It is compatible with C,C++ languages
etc.
 Used in game development, data
base application, web application ,
Artificial Intelligence.
 Lesser time required to learn Pyhton
as it has simple and concise code.

Features of Python
Distinguish between input, output and
error message by different colour
code.
Has large set of libraries with various
module functions.
Has automatic memory management.
Provide interface to all major
databases.

Applications of Python
• Amazon uses python to analyse customer’s
buying habits and search patterns.
• Facebook uses python to process images.
• Google uses python in search system.
• NASA uses python for scientific
programming tasks.
• Python is used in AI systems.

Python Character Set:
• A set of Valid characters that a language can recognize.
• A character set includes:
Letters : A-Z , a-z.
Digits : 0-9
Special Symbols :Space + -*/**(){}[]//!= ==<,>.’’ “”;:%!
White spaces : Blank space ,tabs carriage return ,new
line , form feed.
Other Characters : process all ASCII

Variable
• Has a name
• Capable of storing values of certain
data type.
• Provide temporary storage.

Variable naming conventions
• Variable names are case sensitive.
• Keywords or words with special meanings
should not be used as variables.
• Variable names should be short and
meaningful.
• All variable names should begin with a letter
or underscore(_).
• Variable names may contain numbers,
underscore,.
• no space or special character allowed

Keywords
• Keywords are the words that convey a
special meaning to the language
compiler/interpreter.
• These are reserved for special
purpose.
• Must not be used as normal variables.
• Eg: True, False , if, return , try, elif ,
and ,while, None ,with ,range ,break ,
for ,in ,or

Data Types
• Data types states the way the values of
that type are stored .
• The operations can be done on that
type and the range for that type.
• Different types of data requires different
amount of memory for storage.
• Data can be manipulated through
specific data types.

Standard Data Types
• Numbers
• String
• List
• Tuple
• Dictionary

Number
• Number data type is used to store
numerical values.
• Python support three numerical data
types.
• Integer: eg a=2
• Float: eg: a=2.766
• Complex Numbers: a=17+9b

String
• An order of set of characters closed
in a single or double quotation marks.
• Eg: str1=‘Hello’
• wrd=“Hello”

List
• List is a collection of comma separated
values within square bracket.
• Values in the list can be modified.
• The values in the list are called
elements.
• It is mutable.
• Elements in the list need not be of
same type.

Eg:
• List1=[1,56,84,5]
• List2=[45,98,48,65,0,23]
• List3=[‘anna’,’aby’,’riya’,’diya’]

Tuple
• A tuple is a sequence of comma
separated values . Values in tuple
cannot be changed.
• It is immutable.
• The values in the tuple are called as
elements.
• Elements in the list need not be of
same type.

Eg:
tup1=(‘Sunday’,’Monday’,10,20)
tup2=(10,20,30)
tup3=(‘a’,’b’,’c’,’d’)

Dictionary
• An unordered collection of items where
each item is a key: value pair
• Each key is separated from its value
by a colon (:) .
• The entire dictionary is enclosed within
curly braces {}.
• Keys are unique within dictionary while
the values may not be.

• Eg:
• Dic1={‘R’:RAINY, ‘S’:SUMMER, ‘W’:
WINTER, ‘A’=AUTUMN}

Boolean data type
• The Boolean data type is either TRUE
or FALSE
• In python, Boolean variables are
defined by either True or False.
• The first letter of True and False must
be in upper case . Lower case returns
error

Eg:
>>> a=True
>>> type(a)
<class 'bool'>
>>> a=True
>>> b=False
>>> a or b
True
>>> a and b
False
>>> not a
False
>>> a==b
False
>>> a!=b
True
>>>

Data Type Conversion
• The process of converting the value of
one data type to another data type is
called type conversion.
• There are two types of conversion
• Implicit type conversion
• Explicit type conversion

Implicit type conversion
• In this python automatically convert
one data type to another.
• This process doesn’t need any user
involvement.

Program:
a=50
b=45.5
print('Type of a:',type(a))
print('Type of b:',type(b))
c=a+b
print('Type of c:',type(c))
Output:
Type of a: <class 'int'>
Type of b: <class 'float'>
Type of c: <class 'float'>

Explicit type conversion
• User convert the data type of an object
to the required data type.
• We use predefined functions like int(),
float(),complex(), bool(), str(), tuple(),
list() ,dict() etc to perform explicit type
conversion.
• This type conversion is also known as
type casting.

Input
a=100
b=20.50
c='567'
print('Variable a converted into string:',str(a))
print('Variable a converted into float:',float(a))
print('Variable b converted into integer:',int(b))
print('Variable b converted into string:',str(b))
print('Variable c converted into integer:',int(c))
print('Variable c converted into float:',float(c))
print('Variable a converted into list:',list(c))
OUTPUT
Variable a converted into string: 100
Variable a converted into float: 100.0
Variable b converted into integer: 20
Variable b converted into string: 20.5
Variable c converted into integer: 567
Variable c converted into float: 567.0
Variable a converted into list: ['5', '6', '7']

Operators
• Are special symbols which represent
computation.
• Values or variables are called
oparands .
• The operator is applied on operands,
thus form expression.

Precedence of Arithmetic
operators

User input
• The values inserted by the user while executing a program are
fetched and stored in the variable using the input() function.

User output
• The print statement is used to display
the value of a variable.
• If an expression is given with the print
statement ,it first evaluate the
expression and then print it.
• To print more than one item on a
single line comma (,) can be used.

comments
• A comment in Python starts with the hash
character, # , and extends to the end of the
physical line.
• Comments can be used to explain Python
code.
• Comments can be used to make the code
more readable.
• Comments can be used to prevent
execution when testing code.

Creating a Comment
• Comments starts with a #, and Python will ignore
them:
• Example
• #This is a comment
print("Hello, World!")
• Comments can be placed at the end of a line, and
Python will ignore the rest of the line:
• Example
• print("Hello, World!") #This is a comment
•

• A comment does not have to be text
that explains the code, it can also be
used to prevent Python from executing
code:
• Example
• #print("Hello, World!")
print("Cheers, Mate!")

Multi Line Comments
• Python does not really have a syntax
for multi line comments.
• To add a multiline comment you could
insert a # for each line:
• Example
• #This is a comment
#written in
#more than just one line

• Or, not quite as intended, you can use a
multiline string.
• Since Python will ignore string literals that are
not assigned to a variable, you can add a
multiline string (triple quotes) in your code, and
place your comment inside it:
• Example
• """
This is a comment
written in
more than just one line
"""

Indentation In Python
• Indentation refers to the spaces at the
beginning of a code line.
• Python uses indentation to indicate a block
of code.
• Python will give you an error if you skip the
indentation:
• You have to use the same number of
spaces in the same block of code, otherwise
Python will give you an error:

introduction to python

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