python_class.pptx

Module-1
• Basics of Python:
• Algorithm and Flowchart,
• Elements of Python: Keywords, Identifiers, Variables, Data Types, Features,
• Operators and Expression: Assignment Statements, Numeric Expressions,
Order of Evaluation, Operator Precedence,
• Type, Type Conversations,
• Input Output Statement,
• Comments in Python,
• Sample Program.

What is Python?
• Python is a popular programming language. It was created by Guido
van Rossum, and released in 1991.
It is used for:
• web development (server-side),
• software development,
• mathematics,
• system scripting.

What can Python do?
• Python can be used on a server to create web applications.
• Python can be used alongside software to create workflows.
• Python can connect to database systems. It can also read and modify
files.
• Python can be used to handle big data and perform complex
mathematics.
• Python can be used for rapid prototyping, or for production-ready
software development.

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-oriented way or
a functional way.

Python Syntax compared to other programming languages
• Python was designed for readability, and has some similarities to the
English language with influence from mathematics.
• Python uses new lines to complete a command, as opposed to other
programming languages which often use semicolons or parentheses.
• Python relies on indentation, using whitespace, to define scope; such
as the scope of loops, functions and classes. Other programming
languages often use curly-brackets for this purpose.

Python Install
• To check if you have python installed on a Windows PC, search in the
start bar for Python or run the following on the Command Line
(cmd.exe):
• C:UsersYour Name>python --version
• If you find that you do not have Python installed on your computer,
then you can download it for free from the following
website: https://www.python.org/

The Python Command Line
• To test a short amount of code in python sometimes it is quickest and
easiest not to write the code in a file. This is made possible because
Python can be run as a command line itself.
• Type the following on the Windows, Mac or Linux command line:
C:UsersYour Name>python
• Whenever you are done in the python command line, you can simply
type the following to quit the python command line interface:
exit()

Python Syntax
• Python syntax can be executed by writing directly in the Command
Line:
>>> print("Hello, World!")
Hello, World!
• Or by creating a python file on the server, using the .py file extension,
and running it in the Command Line:
C:UsersYour Name>python myfile.py

Python Indentation
• Indentation refers to the spaces at the beginning of a code line.
• Where in other programming languages the indentation in code is for
readability only, the indentation in Python is very important.
• Python uses indentation to indicate a block of code.
Example:1
• if 5 > 2:
print("Five is greater than two!")
Example:2
• if 5 > 2:
print("Five is greater than two!")
Syntax Error:

Comments
• Python has the commenting capability for the purpose of in-code
documentation.
• Comments start with a #, and Python will render the rest of the line as a
comment:
• Example
• Comments in Python:
• #This is a comment.
print("Hello, World!")
• 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.

Comments
• 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
print("Hello, World!")

Python Variables
• Variables are containers for storing data values.
• In Python, variables are created when you assign a value to it:
• Example
Variables in Python:
x = 5
y = "Hello, World!"
• Python has no command for declaring a variable.

Casting
• If you want to specify the data type of a variable, this can be done
with casting.
• Example
x = str(3) # x will be '3'
y = int(3) # y will be 3
z = float(3) # z will be 3.0

Get the Type
• You can get the data type of a variable with the type() function.
• Example
x = 5
y = “NEW"
print(type(x))
print(type(y))

Single or Double Quotes?
• String variables can be declared either by using single or double
quotes:
• Example
x = “name"
# is the same as
x = ‘name'

Case-Sensitive
• Variable names are case-sensitive.
Example
• This will create two variables:
• a = 4
A = "Sally"
#A will not overwrite a

Variable Names
• A variable can have a short name (like x and y) or a more descriptive name
(age, carname, total_volume).
• Rules for Python variables:
• A variable name must start with a letter or the underscore character
• A variable name cannot start with a number
• A variable name can only contain alpha-numeric characters and underscores (A-z, 0-
9, and _ )
• Variable names are case-sensitive (age, Age and AGE are three different variables)
• Example Legal variable names: Illegal variable names:
myvar = "John"
my_var = "John"
_my_var = "John"
myVar = "John"
MYVAR = "John"
myvar2 = "John"
2myvar = "John"
my-var = "John"
my var = "John"

Multi Words Variable Names
• Variable names with more than one word can be difficult to read.
• There are several techniques you can use to make them more readable:
• Camel Case:
• Each word, except the first, starts with a capital letter:
• myVariableName = "John"
• Pascal Case:
• Each word starts with a capital letter:
• MyVariableName = "John“
• Snake Case:
• Each word is separated by an underscore character:
• my_variable_name = "John"

Python Variables - Assign Multiple Value
• Many Values to Multiple Variables
• Python allows you to assign values to multiple variables in one line:
• Example
• x, y, z = "Orange", "Banana", "Cherry"
print(x)
print(y)
print(z)
• One Value to Multiple Variables
• And you can assign the same value to multiple variables in one line:
• Example
• x = y = z = "Orange"
print(x)
print(y)
print(z)

Unpack a Collection
• If you have a collection of values in a list, tuple etc. Python allows you
to extract the values into variables. This is called unpacking.
• Example
• Unpack a list:
• fruits = ["apple", "banana", "cherry"]
x, y, z = fruits
print(x)
print(y)
print(z)

Output Variables
• The Python print() function is often used to output variables.
• Example
• x = "Python is awesome"
print(x)
• In the print() function, you output multiple variables, separated by a comma:
• Example
• x = "Python"
• y = "is"
• z = "awesome"
• print(x, y, z)
• You can also use the + operator to output multiple variables:
• Example
• x = "Python "
• y = "is "
• z = "awesome"
• print(x + y + z)

Data Types
• Built-in Data Types
• In programming, data type is an important concept.
• Variables can store data of different types, and different types can do different
things.
• Python has the following data types built-in by default, in these categories:
Text Type: str
Numeric Types: int, float, complex
Sequence Types: list, tuple, range
Mapping Type: dict
Set Types: set, frozenset
Boolean Type: bool
Binary Types: bytes, bytearray, memoryview
None Type: NoneType

Getting the Data Type
• You can get the data type of any object by using the type() function:
• Example
• Print the data type of the variable x:
• x = 5
• print(type(x))

Setting the Data Type
• In Python, the data type is set when you assign a value to a variable:
Example Data Type
x = "Hello World" str
x = 20 int
x = 20.5 float
x = 1j complex
x = ["apple", "banana", "cherry"] list
x = ("apple", "banana", "cherry") tuple
x = range(6) range
x = {"name" : "John", "age" : 36} dict
x = {"apple", "banana", "cherry"} set
x = frozenset({"apple", "banana", "cherry"}) frozenset
x = True bool
x = b"Hello" bytes
x = None NoneType

Setting the Specific Data Type
• If you want to specify the data type, you can use the following
constructor functions:
Example Data Type
x = str("Hello World") str
x = int(20) int
x = float(20.5) float
x = complex(1j) complex
x = list(("apple", "banana", "cherry")) list
x = tuple(("apple", "banana", "cherry")) tuple
x = range(6) range
x = dict(name="John", age=36) dict
x = set(("apple", "banana", "cherry")) set
x = frozenset(("apple", "banana", "cherry")) frozenset
x = bool(5) bool
x = bytes(5) bytes

Python Numbers
• There are three numeric types in Python:
• Int: Int, or integer, is a whole number, positive or negative, without decimals, of
unlimited length.
• Float: Float, or "floating point number" is a number, positive or negative, containing
one or more decimals.
• Complex: Complex numbers are written with a "j" as the imaginary part:
• Variables of numeric types are created when you assign a value to them:
• Example
• x = 1 # int
y = 2.8 #float
z = 1j #complex

Python Numbers
• Type Conversion
• You can convert from one type to another with the int(), float(), and complex() methods:
• Example
• Convert from one type to another:
x = 1 # int
y = 2.8 # float
z = 1j # complex
#convert from int to float:
a = float(x)
#convert from float to int:
b = int(y)
#convert from int to complex:
c = complex(x)

Python Numbers
• Python does not have a random() function to make a random
number, but Python has a built-in module called random that can be
used to make random numbers:
• Example
• Import the random module, and display a random number between 1 and 9:
import random
print(random.randrange(1, 10))

Python Numbers
• Python Casting
• Specify a Variable Type
• There may be times when you want to specify a type to a variable. This can be
done with casting. Python is an object-orientated language, and as such it
uses classes to define data types, including its primitive types.
• Casting in python is therefore done using constructor functions:
• int() - constructs an integer number from an integer literal, a float literal (by removing all
decimals), or a string literal (providing the string represents a whole number)
• float() - constructs a float number from an integer literal, a float literal or a string literal
(providing the string represents a float or an integer)
• str() - constructs a string from a wide variety of data types, including strings, integer
literals, and float literals

Python Booleans
• Booleans represent one of two values: True or False.
• Boolean Values
• In programming you often need to know if an expression is True or False.
• You can evaluate any expression in Python, and get one of two answers, True
or False.
• When you compare two values, the expression is evaluated and Python
returns the Boolean answer:

Python Operators
• Operators are used to performing operations on variables and values.
• In the example below, we use the + operator to add together two values:
• Example
• print(10 + 5)
• Python divides the operators in the following groups:
• Arithmetic operators
• Assignment operators
• Comparison operators
• Logical operators
• Identity operators
• Membership operators
• Bitwise operators

Python Arithmetic Operators
• Arithmetic operators are used with numeric values to perform
common mathematical operations:
Operator Name Example
+ Addition x + y
- Subtraction x - y
* Multiplication x * y
/ Division x / y
% Modulus x % y
** Exponentiation x ** y
// Floor division x // y

Python Assignment Operators
• Assignment operators are used to assign values to variables:
Operator Example Same As
= x = 5 x = 5
+= x += 3 x = x + 3
-= x -= 3 x = x - 3
*= x *= 3 x = x * 3
/= x /= 3 x = x / 3
%= x %= 3 x = x % 3
//= x //= 3 x = x // 3
**= x **= 3 x = x ** 3
&= x &= 3 x = x & 3
|= x |= 3 x = x | 3
^= x ^= 3 x = x ^ 3
>>= x >>= 3 x = x >> 3
<<= x <<= 3 x = x << 3

Python Comparison Operators
• Comparison operators are used to compare two values:
Operator Name Example
== Equal x == y
!= Not equal x != y
> Greater than x > y
< Less than x < y
>= Greater than or equal to x >= y
<= Less than or equal to x <= y

Python Logical Operators
• Logical operators are used to combine conditional statements:
Operator Description Example
and Returns True if both statements are true x < 5 and x < 10
or Returns True if one of the statements is
true
x < 5 or x < 4
not Reverse the result, returns False if the
result is true
not(x < 5 and x < 10)

Python Identity Operators
• Identity operators are used to compare the objects, not if they are
equal, but if they are actually the same object, with the same
memory location:
is Returns True if both variables are the
same object
x is y
is not Returns True if both variables are not the
same object
x is not y

Python Membership Operators
• Membership operators are used to test if a sequence is presented in
an object:
in Returns True if a sequence with the
specified value is present in the object
x in y
not in Returns True if a sequence with the
specified value is not present in the object
x not in y

Python Bitwise Operators
• Bitwise operators are used to compare (binary) numbers:
Operator Name Description
& AND Sets each bit to 1 if both bits are 1
| OR Sets each bit to 1 if one of two bits is 1
^ XOR Sets each bit to 1 if only one of two bits is 1
~ NOT Inverts all the bits
<< Zero fill left
shift
Shift left by pushing zeros in from the right and let the leftmost bits fall off
>> Signed right
shift
Shift right by pushing copies of the leftmost bit in from the left, and let the
rightmost bits fall off

Python User Input
• User Input
• Python allows for user input.
• That means we are able to ask the user for input.
• Example:
• username = input("Enter username:")

Types of Expression in Python
1. Constant Expressions:
• A constant expression in Python that contains only constant values is known
as a constant expression.
• In a constant expression in Python, the operator(s) is a constant. A constant is
a value that cannot be changed after its initialization.
• Example :
• x = 10 + 15
• # Here both 10 and 15 are constants but x is a variable.
• print("The value of x is: ", x)

2. Arithmetic Expressions:
• An expression in Python that contains a combination of operators, operands, and
sometimes parenthesis is known as an arithmetic expression.
• The result of an arithmetic expression is also a numeric value just like the
constant expression discussed above.
• Ex:
• x = 10
• y = 5
• addition = x + y
• subtraction = x - y
• product = x * y
• division = x / y
• power = x**y

3. Integral Expressions
• An integral expression in Python is used for computations and type
conversion (integer to float, a string to integer, etc.).
• An integral expression always produces an integer value as a resultant.
• Example:
• x = 10 # an integer number
• y = 5.0 # a floating point number
• # we need to convert the floating-point number into an integer or vice versa for
summation.
• result = x + int(y)
• print("The sum of x and y is: ", result)

4. Floating Expressions:
• A floating expression in Python is used for computations and type
conversion (integer to float, a string to integer, etc.).
• A floating expression always produces a floating-point number as a
resultant.
• Example :
• x = 10 # an integer number
• y = 5.0 # a floating point number
• # we need to convert the integer number into a floating-point number or vice versa
for summation.
• result = float(x) + y
• print("The sum of x and y is: ", result)

5. Relational Expressions:
• A relational expression in Python can be considered as a combination of
two or more arithmetic expressions joined using relational operators.
• The overall expression results in either True or False (boolean result). We
have four types of relational operators in Python (i.e. > , < , >= ,
<=)(i.e.>,<,>=,<=).
• A relational operator produces a boolean result so they are also known as
Boolean Expressions.
• For example :
• 10 + 15 > 2010+15>20
• In this example, first, the arithmetic expressions (i.e. 10 + 1510+15 and 20) are
evaluated, and then the results are used for further comparison.

Types of Expression in Python:
6. Logical Expressions:
• As the name suggests, a logical expression performs the logical
computation, and the overall expression results in either True or False
(boolean result).
• We have three types of logical expressions in Python, let us discuss
them briefly.

7. Bitwise Expressions:
• The expression in which the operation or computation is performed
at the bit level is known as a bitwise expression in Python. The bitwise
expression contains the bitwise operators.
• Example:
• x = 25
• left_shift = x << 1
• right_shift = x >> 1

8. Combinational Expressions:
• As the name suggests, a combination expression can contain a single
or multiple expressions which result in an integer or boolean value
depending upon the expressions involved.
• Example :
• x = 25
• y = 35
• result = x + (y << 1)

Order of Evaluation
• In Python, the left operand is always evaluated before the
right operand.
• That also applies to function arguments.
• Python uses short-circuiting when evaluating expressions
involving the and or operators.
• Python will always evaluate the arithmetic operators first (** is
highest, then multiplication/division, then
addition/subtraction). Next comes the relational
operators. Finally, the logical operators are done last.

Operator Precedence
• Python has well-defined rules for specifying the order in which the
operators in an expression are evaluated when the expression has several
operators. For example, multiplication and division have higher precedence
than addition and subtraction. Precedence rules can be overridden by
explicit parentheses.
Precedence Order
• When two operators share an operand, the operator with the higher precedence
goes first. For example, since multiplication has higher precedence than addition, a +
b * c is treated as a + (b * c), and a * b + c is treated as (a * b) + c.
• Associativity
• When two operators share an operand and the operators have the same
precedence, then the expression is evaluated according to the associativity of the
operators. For example, since the ** operator has right-to-left associativity, a ** b **
c is treated as a ** (b ** c). On the other hand, since the / operator has left-to-right
associativity, a / b / c is treated as (a / b) / c.

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