Introduction to Python and its basics.pdf

Sanjivani Rural Education Society's
Sanjivani College of Engineering, Kopargaon 423603.
-Department of Strucutral Engineering-
By
Mr. Sumit S. Kolapkar (Assistant Professor)
Mail Id- kolapkarsumitst@sanjivani.org.in

Ø What is Language?-
The method of human communication, either spoken or
written, consisting of the use of words in a structured
and conventional way.
Ø What is Computer Language?-
A code or syntax which is used to write programs or any
specific applications. Categories-
Machine Language-
Ø Oldest one
Ø Input is binary input processed by machine (binary
input is in ‘1’ and ‘0’ form)
Ø System needs a compiler and interpreter to convert
the language into computer language so that it can be
processed by a machine.

Machine Language-
Ø Can be directly understood by a central processing
unit (CPU)
Ø The operating system of the computer system is used
to identify the exact machine language used for that
particular system
Ø The operating system defines how the program
should be write so that it can be converted to machine
language and the system takes appropriate action.
Ø The computer programs and scripts can also be
written in other programming languages like C, C++,
and JAVA etc.
Ø However, these languages cannot be directly
understood by a computer system so there is a need
for a program that can convert these computer
programs to machine language.

Machine Language-
Ø The compiler is used to convert the programs to
machine language which can be easily understood by
computer systems.
Ø The compiler generates the binary file and executable
file
Ø Example of machine language for the text “Hello
World”-
01001000 0110101 01101100 01101100 01101111
00100000 01010111 01101111 01110010 01101100
01100100

Assembly Language-
Ø A low-level language for microprocessors and many
other programmable devices
Ø Considered as a second-generation language
Ø Mostly famous for writing an operating system and in
writing different desktop applications.
Ø Is considered as a group of other languages
Ø For any processor, the most used programming
language is assembly language.

High Level Language-
Ø The development of higher-level language is done for
a programmer to write a human-readable program
that can be easily understood by any user.
Ø The syntax used and the programming style can be
easily understood by humans if it is compared to low-
level language.
Ø The only requirement in a high-level language is the
need for a compiler.
Ø Before the execution of high-level programs, it needs
to be converted to machine-level language.
Ø Examples are C++, C, JAVA, FORTRAN, Pascal, Perl,
Ruby, and Visual Basic.

Ø Why Should Learn To Write a Program?-
Ø It helps in speeding up the input and output processes
in a machine.
Ø It is important to automate, collect, manage, calculate,
and analyze the processing of data and information
accurately.
Ø Programming helps to create software and
applications that help computer and mobile users in
daily life.

Ø What is Program?-
Ø A computer program consists of code that is executed
on a computer to perform particular tasks
Ø Programming is the process of giving machines a set
of instructions that describe how a program should be
carried out
Ø Programmers will start by using a code editor or IDE to
write what is called source code
Ø Source code needs to be converted into machine
language so machines can understand the instructions
and execute the program. This process of converting
source code into machine language is known as
compiling
Ø Examples of compiled programming languages would
be C and C++

Ø What is Program?-
Ø There are other languages that do not use compilers.
Instead, these languages will use an interpreter that
will read and execute the code
Ø Examples of interpreted programming languages
would be JavaScript and PHP

Ø The building block of a Program?-
A block is a piece of Python program text that is
executed as a unit.
Ø input
Get data from the “outside world”. This might be reading
data from a file, or even some kind of sensor like a
microphone or GPS. In our initial programs, our input will
come from the user typing data on the keyboard.
Ø output
Display the results of the program on a screen or store
them in a file or perhaps write them to a device like a
speaker to play music or speak text.

Ø The building block of a Program?-
Ø sequential execution
Perform statements one after another in the order they
are encountered in the script.
conditional execution
Check for certain conditions and then execute or skip a
sequence of statements.
Ø repeated execution
Perform some set of statements repeatedly, usually with
some variation.
Ø reuse
Write a set of instructions once and give them a name
and then reuse those instructions as needed throughout
your program.

Ø Computer Hardware Architecture-
The Central Processing Unit (or CPU): Is that part of the
computer that is built to be obsessed with “what is next?”
It executes instructions comprising a computer
program.It performs basic arithmetic, logic, controlling,
and input/output (I/O) operations specified by the
instructions in the program.

The Main Memory: Is used to store information that the
CPU needs in a hurry. The main memory is nearly as
fast as the CPU. But the information stored in the main
memory vanishes when the computer is turned off.

The Secondary Memory: Is also used to store
information, but it is much slower than the main memory.
The advantage of the secondary memory is that it can
store information even when there is no power to the
computer. Examples of secondary memory are disk
drives or flash memory (typically found in USB sticks and
portable music players).

The Input and Output Devices are simply our screen,
keyboard, mouse, microphone, speaker, touchpad, etc.
They are all of the ways we interact with the computer.

Ø What is Python?-
Python is a high-level, general-purpose, self-contained
programming language designed to meet the needs of
computer scientists, software developers, and college
students interested in coding
Ø History of Python-
Is released first in the late 1991 by Guido van Rossum
as 0.9.0
Python 2.0 released on 16 October 2000
Python 3.0, released on 03 December 2008

Ø Features of Python?-
Ø Python is very easy to start programming with and
because of flexible syntax, it can be used to almost
any kind of software application.
Ø Is an open source language that’s free to use.
Ø Interpreted Language
Ø Dynamically Typed Language
Ø Large Standard Library
Ø High-Level Language
Ø Large Community Support
Ø Platform Independent
Ø Extensible and Embeddable
Ø Graphical User Interface (GUI) Support

Ø Reserved Keywords in Python-
Ø It has very special meaning to Python
Ø They have one and only one meaning to Python
Ø Writing meaningful own words that has meaning to us
is called Variables
Ø Has liberty to use any word as a variable but can not
use any Python’s reserved words name as a variable
Ø So the reserved words are those words in the
language where humans talk to Python

Ø Reserved Keywords in Python-

Ø Values andTypes-
A value is one of the basic things a program works with,
like a letter or a number. Ex: 1, 2, or 5.4, or “Hello World!”
Note-
Ø 1, 2 is an integer whereas “Hello World!” is a string.
(strings of letter).
Ø Human being and interpreter can identify strings
easily beacause it is enclosed in a Quotation Marks
Ø 5.4 is the floating point
Types:
Integer (int):-
Is that which does not have any fractional part. The print
statement also works for integers. Contains negative and
positive whole numbers Ex:
>>>print(4)
4

Ø Values andTypes-
Types:
Floating-point:-
Is that which have a fractional part. The print statement
also works for floating point. Ex:
>>>print(4.5)
4.5
OR
>>>print(1.5*4)
6

Ø Values andTypes-
Types:
Complex Numbers with Imaginary parts:-
Is conists of a real part and an imaginary part. Ex:

Ø Values andTypes-
Type of Value by an Interpreter:
>>> type('Hello, World!')
<class 'str'>
>>> type(17)
<class 'int'>
>>> type(3.2)
<class 'float'>
Note-
What about values like “17” and “3.2”?
>>> type('17')
<class 'str'>
>>> type('3.2')
<class 'str'>

Ø Values andTypes-
Type of Value by an Interpreter:
>>> print(1,000,000)
1 0 0
Ø Python interprets 1,000,000 as a comma separated
sequence of integers, which it prints with spaces
between.
Ø Is known as a semantic error.
Ø The code runs without producing an error message,
but it doesn’t do the “right” thing.

Ø Variables-
Ø A variable is a name given to a memory location, that
holds or refers to a value.
Ø It can contain both letters and numbers, but it cannot
start with a number
Ø If we give a variable an illegal name, we will get a
syntax error:
>>> 76trombones = 'big parade'
SyntaxError: invalid syntax
>>> more@ = 1000000
>>> class = 'Advanced Theoretical Zymurgy'

Ø Variables-
• 76trombones is illegal because it begins with a
number
• more@ is illegal because it contains an illegal
character, @
• What went wrong with class as a variable.
It turns out that class is one of Python’s keywords

Ø Character Set-
Ø It is a valid set of all the valid characters/symbols
which can be recognized by the compiler/interpreter
Ø Alphabets- “a to z” OR “A to Z”
Ø Symbols-
Ø Numbers- “0 to 9”
Ø Whitespaces- Blank space, tabs, enter, line feed
(Newline),
Ex-
>>>print(“Hello@123”)
Ø Lexical structure-
Is the set of basic rules that govern how you write
programs in that language.

Ø Tokens (Lexical Units) in Python-
Ø Each logical line (statement) in Python is broken
down into a series of lexical components known as
tokens.
Ø Python converts characters into tokens.
Ø Each token corresponds to a substring of the logical
line.
Note-
• Tokens are the smallest and basic fraction in Python
program.
• Is a set of one or more characters having a meaning
together.

Ø Statements-
Ø A statement is a unit of code (tokens) that the Python
interpreter can execute.
Ø In simple terms, statements are the things you write
to tell Python what your programs should do.
Ø By combining statements, you specify a procedure
that Python performs to satisfy a program’s goals.
Ø Python program structure-
1. Programs are composed of modules.
2. Modules contain statements.
3. Statements contain expressions.
4. Expressions create and process objects.

Ø Types of Tokens-
i. Identifiers,
ii. Keywords,
iii. Operators,
iv. Delimiters, and
v. Literals/Values/Data
Identifiers:-
Is a name used to identify a variable, function, class,
module, or other object.
It aids in distinguishing one entity from others.

Ø Types of Tokens-
Characteristics of Python Identifiers:-
• The initial letter of the identifier should be any letter (A
to Z or a to z) or underscore (_).
• Upper and lower case letters have distinct
characteristics.
• Except for the initial letter, any digit from 0 to 9 can
be part of the identification.
• It shouldn’t be used as a keyword
• Except for the underscore (_), an identifier cannot
contain any special characters such as @, $, and %.
• Identifiers can be as long as you want them to be.
• Case matters when it comes to identifier names.
Myself and myself, for example, are not the same
thing.

Ø Types of Tokens-
Operators:-
Ø Is a special symbol when applied to the variables and
other objects in an expression, cause a computation
or action to occur. There are 7 different operators.
i)Arithmetic Operators-
It performs all the mathematical calculations.
Ex- (+, -, /, *, %,//)

Ø Types of Tokens-
Operators:-
ii) Relational Operator/Comparative Operator-
Examines the relationship between two operands.
Note-
i. Are always in binary form
ii. Results are always in Boolean form (i.e True or
False)

Ø Types of Tokens-
Operators:-
ii) Relational Operator/Comparative Operator-

Ø Types of Tokens-
Operators:-
iii) Assignment Operators-
Employed to allocate a value to a variable. Ex-
• (+=)It adds the right side input to the left side input
and then assigns the result to the left side input.
• (-= )Augmented assignment operator- It takes the
right side operand and subtracts it from the left side
operand, then assigns the result to the left side
operand.
Note-
i. Are always in binary form
ii. Use ‘=’ sign to assign it
iii. Have two values ‘Right-value’ and ‘Left-value’; Right-value
evaluate first then get assign to Left-value

Ø Types of Tokens-
Operators:-
iii) Assignment Operators-

Ø Types of Tokens-
Operators:-
iv) Logical Operators-
Compares the two boolean expressions and yield a
boolean result. Ex-
• The logical and operator makes a condition true if
both operands are true or non-zero.
• The logical or operator returns true if one of the two
operands is true or non-zero.
Note-
i. May be Unary or Binary
ii. Unary logical operator is not and Binary logical
operator is and and or

Ø Types of Tokens-
Operators:-
iv) Logical Operators-

Ø Types of Tokens-
Operators:-
v) Bitwise Operators-
It manipulates individual bits in one or more bit patterns
or binary numbers.
For example, If a binary XOR operator (^) is set in one
input value but not both, it copies the matching binary 1
to the result.
Note-
i. May be Unary or Binary
ii. Unary bitwise operator is only one i.e first
complement (~) and Binary bitwise operator is and
(&), or (|), xor (^), right shift (>>), left shift (<<)
iii. Bitwise operator does not work with string and
floating point.

Ø Types of Tokens-
Operators:-
v) Bitwise Operators-

Ø Types of Tokens-
Operators:-
vi) Membership Operators-
It checks for membership in successions, such as a
string, list, or tuple.
It fetches a variable and if the variable is found in the
supplied sequence, evaluate to true; otherwise, evaluate
to false.
Note-
i. Relational/comparative/arithmetic operators are used
to check values only whereas identity operator (in
and not in) compares “Id” only not a value.
ii. Results are always in Boolean form
iii. Ex:>>>print(2 in [1,2,3,4,5,6])→True
>>>print(2 in [1,3,4,5,6])→False

Ø Types of Tokens-
Operators:-
vi) Membership Operators-

Ø Types of Tokens-
Operators:-
vii) Identity Operators-
When comparing the memory locations of two objects,
identity operators are used. If two variables point to
separate objects, it does not return true; otherwise, it
returns false.
Note-
i. Is a special feature of Python not available in other
languages like C, C++, Java etc.
ii. Relational/comparative/arithmetic operators are used
to check values only whereas identity operator (is
and not is) compares “Id” only not a value.
iii. Results are always in Boolean form

Ø Types of Tokens-
Operators:-
vii) Identity Operators-

Ø Types of Tokens-
Literals:-
• Literals, in Python are the data elements (numeric or
non-numeric) with a fixed value to be store in
variable.
Types of Literals-
i. String Literals (Text Constants)
ii. Numeric Literals. These are further of three types,
integer, float, and complex literals.
iii. Boolean Literals
iv. Literal Collection
Note-
Lists, tuples, dictionaries, and sets are all examples of
literal collections in Python.

Ø Types of Tokens-
Punctuators OR Separators:-
• Punctuators are tokens in python employed to put the
grammar and structure of syntax into practice.
• Punctuators are symbols that are used to structure
programming sentences in a computer language.
• Ex- ‘, ‘ ,#, ,( ) ,{ },[ ] ,@ ,: , =

Ø Operands-
The values that an operator acts on are called operands.
Ø Expression-
A sequence of operands and operators is called an
expression

Ø Difference between Expression and
Statement-
Expression-
An expression is a combination of values(Constants),
variables and operators.
An expression may also include call to functions and
objects.
Any expression evaluates to a single value, which
becomes the value of the expression.
Ex:-
a = 10 # This is an assignment statement
b = 10 # This is an assignment statement
print(a + b) # a + b is an expression and print(a + b) is a
statement

Ø Difference between Expression and
Statement-
Statements-
A statement in Python is a logical instruction which can
be read and executed by Python interpreter. Types are-
i. Print statements
ii. Assignment statements
iii. Selective statements
iv. Iterative statements
v. Function declaration statements

Ø Order of operations in Python-
• When more than one operator appears in an
expression, the order of evaluation depends on the
rules of precedence
• The acronym PEMDAS is a useful way to remember
the rules:
Ø Parentheses have the highest precedence.
Ø Expressions in parentheses are evaluated first, 2 * (3-
1) is 4, and (1+1)**(5-2) is 8.
Ø Even we can use parentheses to make an expression
easier to read, as in (minute * 100) /60, even if it
doesn’t change the result.
Ø Exponentiation has the next highest precedence, so
2**1+1 is 3, not 4, and 3*1**3 is 3, not 27.

Ø Multiplication and Division have the same precedence,
which is higher than Addition and Subtraction, which
also have the same precedence. So 2*3-1 is 5, not 4,
and 6+4/2 is 8, not 5.
Ø Operators with the same precedence are evaluated
from left to right. So the expression 5-3-1 is 1, not 3,
because the 5-3 happens first and then 1 is
subtracted from 2.
Note-
When in doubt, always put parentheses in your
expressions to make sure the computations are
performed in the order you intend.

Example:- (43+13−9/3∗ 7)
i. From left to right, 9/3∗ 7= 3∗ 7= 21
ii. Expression has become, 43+13−21
iii. Left to right Associativiy rule will be followed again.
So, the final value of expression will be-
43+13−21 = 56−21= 35

Introduction to Python and its basics.pdf

Recommended

More Related Content

Recently uploaded (20)

Featured (20)

Introduction to Python and its basics.pdf