1. PGA2.0-Python Programming-Intro to Python.pptx

Python
Programming
Introduction to Python
02-10-2022 Dr. Poonam Panwar, Associate Professor, CUIET 1

Agenda
In this session, you will learn about:
• Introduction to Python
• Variables
• Functions
• Python Operators
• Python Flow Controls
• Conditional Statements
• Loops

Introduction to Python
Dr. Poonam Panwar, Associate
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Some Common Languages in use
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Languages History
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History of Python
• First public release in 1991
• Open source from beginning
• Managed by Python Software
Foundation
Invented in December 1989
Guido Van Rossum
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Python
Python drew inspiration from other programming languages:
Python is powerful... and fast;
plays well with others;
runs everywhere;
is friendly & easy to learn;
is Open.
Python is an interpreted language, do not need to be compiled to run.
Python is a high-level language, which
means a programmer can focus on
what to do instead of how to do it.
Writing programs in Python takes less
time than in another language.
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Python Used For
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Compiling and Interpreting
Many languages are required to compile the program into a form (ByteCode) that
the machine understands.
Python is instead directly interpreted into machine instructions.
compile execute
output
source code
Hello.java
byte code
Hello.class
interpret
output
source code
Hello.py
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Development Environment
Terminal /
Shell based
Three most common options:
iPython notebook
IDLE (Spyder
IDE)
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Anaconda
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Anaconda Navigator
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Jupyter IDE
Click here to change the name of
the notebook
Write your code
here
Menu bar
Running Python
Kernel
Execute the
code using Run
button or
shift+enter

Jupyter IDE
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Spyder IDE
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A Python Code Sample
Assignment uses = and comparison uses ==
For numbers +-*/% are as expected
Logical operators are words (and, or, not)
The basic printing command is print
Start comments with #: the rest of line is ignored
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Variables
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Variables
Variables are reserved memory that store data
Unlike languages like C,
C++ and Java, Python
has no command for
declaring variable
= operator is used to
assign a value to a
variable

We would only receive the second assigned value as the
output since that was the most recent assignment
Reassigning Variables

Reassigning Variables
You can connect a different value with a previously
assigned variable very easily through simple reassignment

Multiple Variable Assignment
With same value

Multiple Variable Assignment
With different values

Data Types
String Numeric Boolean None Collection
Integer Float
List Tuple Dictionary Set
Data Types in Python

Data Types
String Numeric Boolean None Collection
Integer Float
List Tuple Dictionary Set
We will learn the following data types today

String variables are variables that hold zero or more characters such as letters,
numbers, spaces, commas and many more
Creating String Variables
Use type(variable_name) to check the data type of variable declared

Creating Numeric Variables
As seen earlier, there are two types of
numeric data types:
Integer Float
A numeric variable is one that may take on any value within a finite or infinite interval

Creating Boolean Variables
Boolean variables are variables that
can have only two possible values:
True False

Data Type Conversion
Type Conversion
Implicit
Conversion
Explicit
Conversion
Python supports conversion of one data type to another

Data Type Conversion
Type Conversion
Implicit
Conversion
Explicit
Conversion
Arithmetic
Operation
Casting
Operation
Implicit Conversion: Conversion done by Python interpreter without
programmer’s intervention
Explicit Conversion: Conversion that is user-defined that forces an expression
to be of specific data type

Implicit Conversion
In Implicit Conversion, the conversion is done by Python interpreter without
programmer’s intervention

Explicit Conversion
In Explicit Conversion, conversion that is user-defined forces an expression to be
of specific data type
Example

Explicit Conversion
Explicit data type
conversion using float()
function

Type Casting
Type Casting
float() bool() str()
int()

Functions
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What are Functions?
A function is a block of reusable code that runs when called
Function name: sum()
Input
parameters
Return value
of the function
• A function has a name. You call the function by its name
• A function can take input(s), known as input parameters
• A function can return data as a result

What are Functions?
There are three types of functions:
Built-in
Functions
User-defined
Functions
Lambda
Functions
Some of the built-in functions are:
print() - to print the output
input() - to take input from user
the type casting functions like int(), float(), str(), bool(), etc.
We will study the user-defined functions and lambda
functions in detail in our upcoming sessions

The print() function prints the specified message to the screen
The message can be a string, or any other object
The object will be converted into a string before written to the screen
The print() in Python
strings separated by a comma within a
print() function get concatenated.
strings separated by a
comma within a print()
function get concatenated.

The print() in Python
The sep is an optional
parameter. When output is
printed, each word is
separated by comma and
space character
print(‘n’) gives a new
blank line
The backslash “” is a special character that represents whitespaces. For
example ‘t’ is a tab and ‘n’ is a new line.

Invalid use of opening and closing quotes is not allowed.

Concatenation using print()
Use + operator to
concatenate two
strings

Adding numbers to strings does not make any sense. Please consider explicit
conversion to convert the number to string first, in order to join them together.
You cannot concatenate string & number.

Concatenation with Type Casting
Explicit conversion of a number to
string with str() function.
We learn more such type conversions in our upcoming sessions

Python Operators
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Python Operators
The Python Operators are:
Arithmetic
Operators
Relational Operators Logical Operators
Membership
Operators
Bitwise Operators
Assignment
Operators
The Python Operators are:

Python Operators
The most common Arithmetic Operators are:
Addition Subtraction Multiplication
Division Modulus Floor Division
exponentiation
+ - *
/ % //
**

Arithmetic Operators
Addition
Note that 22 is a string
Here two strings are getting
concatenated

Subtraction

Subtraction
When two strings are added, the + (addition) operator basically
concatenates the two strings. Subtracting two strings does not make
any sense.

Multiplication

Floor Division

Exponentiation

Relational operators are used to compare values and take certain decisions based
on the outcome
Relational Operators
Following are some of the relational operators:
Operators Meaning
< Is less than
<= Is less than & equal to
> Is greater than
>= Is greater than & equal to
== Is equal to
!= Is not equal to

Logical operators in Python allow a program to make a decision based
on multiple conditions
Each operand is considered a condition that can be evaluated to a true
or false value
Logical Operators
Returns True if
both the
operands are
true
AND
Returns True if
either of the
operands are
True
OR
Returns true if
the operand is
false
NOT

Logical Operators
AND
If both the operands are true then it returns true

Logical Operators
OR
If one of the operands are true then it returns true

Logical Operators
NOT
Reverses the result

Membership Operators
Membership operators checks whether a value is a member of a sequence.
The sequence may be a list, a string, a tuple, or a dictionary
in
• The ‘in’ operator is
used to check if a
value exists in any
sequence object or
not
not in
• A ‘not in’ works in an
opposite way to an
‘in’ operator. A ‘not
in’ evaluates to True
if a value is not
found in the
specified sequence
object. Else it
returns a False.

Python Bitwise Operators take one to two operands, and operates on it/them
bit by bit, instead of whole
Some Bitwise Operators
& (Bitwise and)
• The binary and (&) takes two values and performs
an AND-ing on each pair of bits.
| (Bitwise or)
• Compared to &, this one returns 1 even if one of the
two corresponding bits from the two operands is 1.

Truth Tables
| (Bitwise or)
& (Bitwise and)

Some Bitwise Operators
| operator
& operator
Example
(10 % 2 == 0) & (10 % 3 == 0) (10 % 2 == 0) | (10 % 3 == 0)
Implies True & False. This results in False. Implies True | False. This results in True.

The assignment operators are used to store data into a variable
More Assignment Operators

Python Flow Controls
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Python Flow Control
Any program has a flow and the flow is the order in which the program’s
code executes
The control flow of a Python program is controlled by:
Conditional
Statements
Loops
Function
Calls
We cover the basics of conditional statements and
loops in today’s session

Conditional Statements
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● The if statement is used in Python for decision making
● It is written by using the if keyword
● The if keyword is followed by condition later followed by
indented block of code which will be executed only if the
condition is true
Syntax:
if
(condition):
statement(s)
The if-statement
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The if-statement
Example
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● The ‘if..else’ statement evaluates a test expression and will
execute:
o the indented if block of code if the condition is True
o the indented else block of code if the condition in the if
statement is False
The if-else statement
Syntax:
if (condition):
Body of if
else:
Body of else
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The if-else statement
Example
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Elif statement is used to control multiple conditions only if the given if
condition is false
The if elif else statement
Syntax:
if (condition1):
Body of if
elif (condition2):
Body of elif
elif (condition3):
Body of elif
.
.
.
else:
Body of
else
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The if elif else statement
Example
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● Nesting means using an if statement within another if
statement
● If the first ‘if’ condition is satisfied then the program executes
the commands within that ‘if’
Nested if-else statement
Syntax:
if (condition):
statement(s)
if (condition):
statement(s)
else:
statement(s)
else:
statement(s)
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Example
Nested if-else statement
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Example
Nested if statement
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Loops
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● Loops are used to execute of a specific block of code repetitively
● The ‘while loop’ in Python is used to iterate over a block of code as long as
the test expression holds true
● This loop is used when the number of times to iterate is not known to us
beforehand
While loop
Syntax:
while (condition):
Body of while
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Example
While loop
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● The ‘for loop’ in Python is used to iterate over the items of a sequence
object like list, tuple, string and other iterable objects
● The iteration continues until we reach the last item in the sequence object
The for Loop
Syntax:
for i in sequence:
Body of for
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Example
The for Loop
Iteration is a general term for taking each item from a sequence one after
another
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Loops in Python allows us to repeat tasks
Getting out of a Loop
Exit a loop completely when a certain condition is triggered
But at times, you may want to:
Skip part of a loop and start next execution
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• The ‘break’ statement ends the loop
and resumes execution at the next
statement
• The break statement can be used in
both ‘while’ loop and ‘for’ loop
• It is always used with conditional
statements
Getting out with Break Statement
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Getting out with Break Statement
Example
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• The ‘continue’ statement in Python
ignores all the remaining
statements in the iteration of the
current loop and moves the control
back to the beginning of the loop
• The continue statement can be used
in both ‘while’ loop and the ‘for’
loop
• Like break, continue is also always
used with conditional statements
Skip Loop Step with Continue Statement
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Skip Loop Step with Continue Statement
Example
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Nested for Loop
for [first iterating variable] in [outer loop]:
[code line 1]
[code line 2]
for [second iterating variable] in [nested loop]:
[code line 1]
1st level loop or outer
loop
Nested loop
1st indentation
2nd indentation
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Nested for Loop
Outer loop
Inner loop
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Thank you
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