What is Python

Python is a high-level, interpreted programming language that is known for its simplicity, readability, and ease of use. It is used for a wide range of applications, including web development, data analysis, artificial intelligence, and automation. Python's syntax is designed to be easy to understand, which makes it a popular choice for beginners and experts alike. One of Python's strengths is its vast collection of libraries and frameworks, which provide a wide range of tools for developers to use in their projects.

Installing Python

To install Python on your machine, you can go to the official Python website and download the appropriate version for your operating system. Once downloaded, follow the installation instructions and Python will be ready to use on your machine.

Getting Python IDE on most of the OS.

Download Python

Information about specific ports, and developer info Source and binary executables are signed by the release manager or binary builder using their OpenPGP key.

www.python.org

Python version 2

Version	Operating System	Description	MD5 Sum	File Size	GPG
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macOS 64-bit installer	macOS	for OS X 10.9 and later	ce98eeb7bdf806685adc265ec1444463	24889285	SIG
Windows debug information files	Windows		20b111ccfe8d06d2fe8c77679a86113d	25178278	SIG
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Windows help file	Windows		b3b753dffe1c7930243c1c40ec3a72b1	6322188	SIG
Windows x86-64 MSI installer	Windows	for AMD64/EM64T/x64	a425c758d38f8e28b56f4724b499239a	20598784	SIG
Windows x86 MSI installer	Windows		db6ad9195b3086c6b4cefb9493d738d2	19632128	SIG

Python version 3 [Release Date: Sept. 6, 2022]

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macOS 64-bit universal2 installer	macOS	for macOS 10.9 and later	4c89649f6ca799ff29f1d1dffcbb9393	40865361	SIG	CRT
Windows embeddable package (32-bit)	Windows		7e4de22bfe1e6d333b2c691ec2c1fcee	7615330	SIG	CRT
Windows embeddable package (64-bit)	Windows		7f90f8642c1b19cf02bce91a5f4f9263	8591256	SIG	CRT
Windows help file	Windows		643179390f5f5d9d6b1ad66355c795bb	9355326	SIG	CRT
Windows installer (32-bit)	Windows		58755d6906f825168999c83ce82315d7	27779240	SIG	CRT
Windows installer (64-bit)	Windows	Recommended	bfbe8467c7e3504f3800b0fe94d9a3e6	28953568	SIG	CRT

Variables

Variables are an essential concept in programming, and Python is no exception. In Python, a variable is a container that stores a value, such as a number, string, or list. These values can be changed or manipulated throughout a program, making variables a powerful tool for building complex applications. In this section, we will explore how to declare and use variables in Python and learn about different data types that can be stored in a variable.

In Python, there are several variable types, including:

• Integers (int)
• Floating-point numbers (float)
• Booleans (bool)
• Strings (str)
• Lists (list)
• Tuples (tuple)
• Dictionaries (dict)
• Sets (set)

Variables can also be assigned the value of None, which represents the absence of a value. Here is an example of Integer, Float, and String variable in Python.

# Declare a variable 'age' and assign it the value 25
age = 25

# Declare a variable 'y' and assign it the value 3.14
y = 3.14

# Declare a variable 'name' and assign it the value "John"
name = "John"

# Print the value of 'age'
print(age)

# Print the value of 'y'
print(y)

# Print the value of 'name'
print(name)

In this example, we declare three variables: age, y, and name. We assign the value 25 to age, the value 3.14 to y, and the value "John" to name. We then print the values of age, y, and name to the console using the print() function.

The output of the program will be:

25
3.14
John

This demonstrates how to declare and use variables in Python, and shows some of the different data types that can be stored in a variable (integer, float, and string).

Strings

In Python, a string is a sequence of characters enclosed in quotation marks. Python allows strings to be enclosed in either single quotes ('...') or double quotes ("..."). Strings can be used to represent text, numbers, or other types of data.

Here are some examples of how to declare and use strings in Python:

# Declare a string variable 'name' and assign it the value "Alice"
name = "Alice"

# Declare a string variable 'message' and assign it the value "Hello, world!"
message = 'Hello, world!'

# Print the value of 'name'
print(name)

# Print the value of 'message'
print(message)

# Concatenate two strings
greeting = "Hello"
name = "Alice"
full_greeting = greeting + " " + name
print(full_greeting)

# Access individual characters in a string
word = "Python"
first_letter = word[0]
last_letter = word[-1]
print(first_letter)
print(last_letter)

In this example, we declare two string variables: name and message. We assign the value "Alice" to name and the value "Hello, world!" to message. We then print the values of name and message to the console using the print() function.

We also show how to concatenate two strings using the + operator, and how to access individual characters in a string using indexing. Finally, we print the first and last characters of the string "Python".

The output of the program will be:

Alice
Hello, world!
Hello Alice
P
n

This demonstrates how to declare and use strings in Python, including how to concatenate strings and access individual characters in a string using indexing.

Here are some commonly used string methods in Python:

• count(substring): Returns the number of occurrences of a substring in a string. Example: "hello world".count("l") will return 3.
• find(substring): Returns the index of the first occurrence of a substring in a string, or 1 if the substring is not found. Example: "hello world".find("l") will return 2.
• upper(): Returns the string in all uppercase letters. Example: "hello world".upper() will return "HELLO WORLD".
• lower(): Returns the string in all lowercase letters. Example: "HELLO WORLD".lower() will return "hello world".
• replace(old, new): Replaces all occurrences of a substring in a string with a new substring. Example: "hello world".replace("l", "L") will return "heLLo worLd".
• split(delimiter): Splits a string into a list of substrings based on a delimiter. Example: "hello,world".split(",") will return ["hello", "world"].

These are just a few examples of the many methods available for manipulating strings in Python.

Data Structure

Conditional Statement

In Python, conditional statements are used to execute different parts of code depending on the truth value of a condition. The most common conditional statements in Python are if, elif, and else.

if statement

The if statement is used to execute a block of code if a condition is true. Here is the syntax for the if statement:

if condition:
    # code to execute if condition is true

The code block under the if statement is executed only if the condition is true. If the condition is false, the code block is skipped.

Here is an example:

age = 18

if age >= 18:
    print("You are old enough to vote.")

In this example, the if statement checks if the age variable is greater than or equal to 18. If it is, the message "You are old enough to vote." is printed to the console.

elif statement

The elif statement is used to check for additional conditions after the if statement. Here is the syntax for the elif statement:

if condition1:
    # code to execute if condition1 is true
elif condition2:
    # code to execute if condition2 is true

The code block under the elif statement is executed only if the if statement is false and the elif condition is true. If the elif condition is false, the code block is skipped.

Here is an example:

age = 16

if age >= 18:
    print("You are old enough to vote.")
elif age >= 16:
    print("You can drive, but you cannot vote.")

In this example, the if statement checks if the age variable is greater than or equal to 18. If it is, the message "You are old enough to vote." is printed to the console. If the if statement is false, the elif statement checks if the age variable is greater than or equal to 16. If it is, the message "You can drive, but you cannot vote." is printed to the console.

else statement

The else statement is used to execute a block of code if all the previous conditions are false. Here is the syntax for the else statement:

if condition1:
    # code to execute if condition1 is true
elif condition2:
    # code to execute if condition2 is true
else:
    # code to execute if all conditions are false

The code block under the else statement is executed only if all the previous conditions are false.

Here is an example:

age = 14

if age >= 18:
    print("You are old enough to vote.")
elif age >= 16:
    print("You can drive, but you cannot vote.")
else:
    print("You are not old enough to drive or vote.")

In this example, the if statement checks if the age variable is greater than or equal to 18. If it is, the message "You are old enough to vote." is printed to the console. If the if statement is false, the elif statement checks if the age variable is greater than or equal to 16. If it is, the message "You can drive, but you cannot vote." is printed to the console. If both the if and elif statements are false, the else statement prints the message "You are not old enough to drive or vote." to the console.

These are just a few examples of how conditional statements can be used in Python. They can be combined in many different ways to create complex programs.

Switch Statement

Python does not have a switch statement like some other programming languages, but the same functionality can be achieved using if and elif statements.

Here is an example of how to use if and elif statements to achieve the same functionality as a switch statement:

def switch_case(case):
    if case == 1:
        print("Case 1")
    elif case == 2:
        print("Case 2")
    elif case == 3:
        print("Case 3")
    else:
        print("Invalid case")

switch_case(1) # prints "Case 1"
switch_case(2) # prints "Case 2"
switch_case(3) # prints "Case 3"
switch_case(4) # prints "Invalid case"

In this example, the switch_case() function takes a single argument case. The function uses if and elif statements to check the value of case and execute the corresponding block of code. If case does not match any of the specified values, the function prints "Invalid case".

This demonstrates how to achieve the same functionality as a switch statement in Python using if and elif statements.

Differences between if condition and switch condition

An "if" condition is a conditional statement that executes a block of code if a specified condition is true. A "switch" condition is a conditional statement that evaluates an expression and executes code as per the matched case label. While "if" conditions are generally used for simple, straightforward comparisons, "switch" conditions can be more useful for complex comparisons or when multiple cases need to be evaluated.

Please Excuse My Dear Aunt Sally [order of operation in Python and called PEMDAS]

() Parentheses

^ Exponent

x Multiplication

/ Division

+ Addition

- Subtraction

Examples:

(1 + 2) * 3 ⇒ 6

( True or True ) and False ⇒ False

Loops

Functions

Classes / Objects

Libraries

Read From a File

Write to a File

Read an Input from a User