Lecture-1

Introduction
to
Python Programming
 Table of Contents
▪ Introduction to Python
▪ Variable
▪ Arithmetic Operator
▪ Using of Print
▪ Input from User
▪ Objects and Dynamic Typing.
(Ref. Text, 50-70)

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 Introduction to Python
• Python is an interpreted, interactive, object-oriented, and
high-level programming language developed in early 90’s.
• Python is a general purpose programming language that is
often applied in scripting roles.
• Python is designed to be highly readable. It uses English
keywords frequently whereas other languages use
punctuation, and it has fewer syntactical constructions than
other languages.

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 History
• Invented in the Netherlands, early 90s by Guido
van Rossum. Python was conceptualized in the
late 1980s and its implementation was started in
December 1989.
• Guido Van Rossum is fan of ‘Monty Python’s
Flying Circus’, a famous TV show in Netherlands,
So he named Python after Monty Python.
• Nearly all known Python software initially
developed by Guido van Rossum and released in
1991.
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Difference of Programing & Scripting Language
Programming Scripting
• a program is executed (i.e. the • a script is interpreted A "script" is
source is first compiled, and the code written in a scripting
result of that compilation is language.
expected) • A scripting language is nothing but
• A "program" in general, is a a type of programming language
sequence of instructions written in which we can write code to
so that a computer can perform control another software
certain task. application.

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 Scope of Python
• Science
-Bioinformatic
-Artificial Intelligence
• System Administration
• Web Application Development
-CGI
• Software Development
• System Scripting.
• Gaming, Robotics and more

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 Why Python ?
• Python works on different platforms (Windows, Mac, Linux,
Raspberry Pi, (etc.)
• Python has a simple syntax similar to the English language.
• Python has syntax that allows developers to write programs with
fewer lines than some other programming languages.
• Python runs on an interpreter system, meaning that code can be
executed as soon as it is written. This means that prototyping can
be very quick.
• Python can be treated in a procedural way, an object-orientated
way or a functional way.
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 Python Code Execution
• Python’s traditional runtime execution model: source code you
type is translated to byte code, which is then run by the Python
Virtual Machine. Your code is automatically compiled, but then
it is interpreted.

Source code extension is .py

Byte code extension is .pyc (compiled python code)

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 Syntax of Python
>>> print("Hello World!")
Hello World!
>>> 2+3
5
Relevant output is displayed on subsequent lines without the >>> symbol
Once you install any of the Python IDE, you can type code easily then before.
Example:
print (“Hello world!”)
Output: Hello world!
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 Variables in Python
Variables are containers for storing data values. Python has no
command for declaring a variable. A variable is defined the
moment you assign a value in it. Depending on the value the
variable types is define.
Example:
x = 40 # x is of type int
x = "Bangladesh" # x is now of type str
print(x)
Print(type(x))

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 Built-in Data Types
Formation Data Types
Text Types: str
Numeric Types: Int, float, complex
Sequence Types: List, tuple, range
Mapping Types: dict
Set Types: Set, frozenset
Boolean Types: bool
Binary Types: bytes, bytearray, memoryview

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 Arithmetic operators
OPERATOR DESCRIPTION SYNTAX
+ Addition: adds two operands x+y
- Subtraction: subtracts two operands x-y
* Multiplication: multiplies two operands x*y
Division (float): divides the first operand by the
/
second
x/y
Division (floor): divides the first operand by the
//
second
x // y
Modulus: returns the remainder when first operand
%
is divided by the second
x%y
** Power : Returns first raised to power second x ** y
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 Relational Operators
OPERATOR DESCRIPTION SYNTAX
Greater than: True if left operand is greater
> than the right x>y
Less than: True if left operand is less than
< the right x<y
== Equal to: True if both operands are equal x == y
!= Not equal to - True if operands are not equal x != y
Greater than or equal to: True if left operand
>= is greater than or equal to the right x >= y
Less than or equal to: True if left operand is
<= less than or equal to the right x <= y

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 Assignment operators
OPERATOR DESCRIPTION SYNTAX

= Assign value of right side of expression to left side operand x=y+z

Add AND: Add right side operand with left side operand and then assign to
+= a+=b a=a+b
left operand
Subtract AND: Subtract right operand from left operand and then assign to
-= a-=b a=a-b
left operand
Multiply AND: Multiply right operand with left operand and then assign to
*= a*=b a=a*b
left operand
Divide AND: Divide left operand with right operand and then assign to left
/= a/=b a=a/b
operand
Modulus AND: Takes modulus using left and right operands and assign result
%= a%=b a=a%b
to left operand
Divide(floor) AND: Divide left operand with right operand and then assign the
//= a//=b a=a//b
value(floor) to left operand

Exponent AND: Calculate exponent(raise power) value using operands and

**= a**=b a=a**b
assign value to left operand

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 Print Function
The built-in print function displays its argument(s) as a line of text:
In [1]: print('Welcome to Python!’)
Welcome to Python!

Printing a Comma-Separated List of Items

In [2]: print('Welcome', 'to', 'Python!’)
Welcome to Python!

Printing Many Lines of Text with One Statement, When a backslash (\)
appears in a string, it’s known as the escape character.
In [3]: print('Welcome\nto\n\nPython!’)
Welcome
To
Python!
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 Other Escape Sequences
Escape sequence Description
Insert a newline character in a string. When the string is
\n displayed , for each newline, move the screen cursor to the
beginning of the next line.
Insert a horizontal tab. When the string is displayed, for each
\t tab, move the screen cursor to the next tab stop.
\\ Insert a backslash character in a string.

\” Insert a double quote character in a string.

\’ Insert a single quote character in a string.

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Printing Expression with Escape Sequences
In [1]: print('Sum is', 7 + 3)
Sum is 10

In [2]: print('Display \'hi\' in quotes’)

Display 'hi' in quotes

Ln [3]: print("Display \"hi\" in quotes")

Display "hi" in quotes

In [4]: print("""Display "hi" and 'bye' in quotes""")

Display "hi" and 'bye' in quotes

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 Getting Input from the User
In [1]: name = input("What's your name? ")
What's your name? Paul
In [2]: print(name)
Paul

In [3]: value1 = input('Enter first number: ‘)

Enter first number: 7
In [4]: value2 = input('Enter second number: ‘)
Enter second number: 3
In [5]: add = value1 + value2
Out[6]: print(add)
73
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 Multiple Input from the User
In [1]: a , b = input().split()
5 10
In [2]: Print(a , b)
5 10
In [3]: Print(type(a))
<class ‘str’>

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 Objects and Dynamic Typing
• In [1]: type(7)
• Out[1]: int
• In [2]: type(4.1)
• Out[2]: float
• In [3]: type('dog')
• Out[3]: str

Values such as 7 (an integer), 4.1 (a floating-point number) and 'dog' are
all objects. Every object has a type and a value. An object’s value is the
data stored in the object. The snippets above show objects of Python
built-in types int (for integers), float (for floating-point numbers) and str
(for strings).

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 Variables Refer to Objects
Assigning an object to a variable binds (associates) that variable’s name to the object. As
you’ve seen, you can then use the variable in your code to access the object’s value:
• In [4]: x = 7
• In [5]: x + 10
• Out[5]: 17
• In [6]: x
• Out[6]: 7

After snippet [4]’s assignment, the variable x refers to the integer object containing 7. As
shown in snippet [6], snippet [5] does not change x’s value. You can change x as follows:
• In [7]: x = x + 10
• In [8]: x
• Out[8]: 17

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 Dynamic Typing
Python uses dynamic typing—it determines the type of the object a
variable refers to while executing your code. We can show this by
rebinding the variable x to different objects and checking their types:
• In [9]: type(x)
• Out[9]: int
• In [10]: x = 4.1
• In [11]: type(x)
• Out[11]: float
• In [12]: x = 'dog'
• In [13]: type(x)
• Out[13]: str

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 Getting Your Questions Answered
Online forums enable you to interact with other Python
programmers and get your Python questions answered. Popular
Python and general programming forums include:

• python-forum.io
• StackOverflow.com
• https://www.dreamincode.net/forums/forum/29-python/
• Colab Notebook for lab

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Thank You

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