Introduction to Python Programming

Introduction

• The lecture is for students in the beginning stages of programming or Python.
• Students can prepare for college placements, competitive coding, web development (Django), AI, machine learning, and data science after this video.

Requirements

• A laptop and excitement are needed.

Installation (Windows)

• Python 3.7 can be downloaded from python.org; the website link is in the notes.
• Install Python by opening and executing the downloaded file.

Running Python Code

• Use the print function to output statements.
• Comments are highlighted lines not included in the code.
• Functions are code parts performing operations, written with parentheses ().
• Text in Python is written in quotes.

Text Formatting

• Strings can use single or double quotes.
• Double quotes are preferred for strings (like Java/C++), and single quotes for characters.
• Click the green run button to run the code.
• Save code in a file (File -> Save As) with a .py extension (e.g., first_prog.py).

PyCharm Overview

• Used due to the virtual machine limitation.
• Install and open PyCharm by dragging it to the applications folder.
• Keep default settings while opening.

Creating a New Project (PyCharm)

• Open the software to see a window.
• Different projects can be created, each holding multiple Python files.
• Create a new project and name it (e.g., "College").

Project Location

• The path before the project name shows where project files will be saved.
• Choose an environment (can be ignored for beginners).

Base Interpreter

• The base interpreter (Python) can be chosen.
• The computer may have other Python versions.
• If options don't appear, directly create the project.

Creating a Python File

• Right-click, go to New, and select Python File.
• Name the file (e.g., "First Program").
• Code can be written in the opened file, named first_prog.py.

Introduction to Python Files

• Python files end with .py.
• Files such as d_txcindia.gov.in might be related to Java-style extensions elsewhere.
• Virtual environments store Python-specific files.

Focusing on a Single Python File

• Users can hide irrelevant files in environments with multiple Python files.
• Hiding files helps focus on the current coding task.

Outputting in Python

• The print function displays output.
• Parentheses () follow print, enclosing what to display.
• "Hello World" example demonstrates printing a string.

Strings in Python

• Strings are text characters enclosed in double quotes.
• Strings are immutable text that remains as typed.

Case Sensitivity in Python

• Python is case-sensitive; print (lowercase p) is different from Print.
• Incorrect case leads to errors because Python won't recognize undefined commands.

Functions like Print

• Parentheses signify print as a function.
• Functions execute actions in Python; creation and use are covered later.

Running Code

• Run code via the "Run" option in the interface.
• The output appears in an output screen.

Keyboard Shortcuts

• Keyboard shortcuts like Ctrl+Shift+R speed up coding.
• Shortcuts vary by OS; macOS has Ctrl+Shift+R, Windows has different ones.

Variables

• Variables store data in memory locations.
• Memory locations are assigned names, called variables, for easy reference.

Variable Naming and Storage

• Example: name = "string" stores a name.
• age = number stores a number.

Printing Variables

• Printing a variable like name displays its stored value.
• Quoting name would print "name" as a literal string.

Value Changing

• Variable values can be modified after initial assignment.
• Updated values are reflected in subsequent print statements.

Types of Variables

• String: Text inside quotes.
• Number: Integer (whole number).
• Floating Number: Number with decimal points (e.g., 24.0).
• Boolean: Represents truthiness (True or False).

Booleans

• Boolean variables are True or False.
• Case-sensitive: True must start with a capital T.

Python's Flexibility in Variable Declaration

• Python doesn't require pre-declaration of variable types.
• Variables adapt to the type of data assigned to them.

Variable Name Rules

• Naming conventions may allow underscores.
• Specific rules for variable naming are in the associated notes.

Exercise

• Define a person: first name "Tony," last name "Stark."
• Create an "age" variable as 51.
• Define an "is_genius" Boolean variable.
• Solution is available in the provided notes.

User Input

• input() function takes input from the user.
• Example: input("What is your name?").

Storing Input

• Store input in a variable: name = input("What is your name?").
• Use the stored variable to print: print(name).

Concatenation

• Concatenate strings using the + operator.
• Example: "Hello " + name combines two strings.
• Concatenation joins strings together.

Superhero Exercise

• Prompt for a superhero name.
• Store the input.
• Print the entered name.
• Solution is in the notes.

Type Conversion

• Input is always received as a string.
• Conversion is needed for numerical operations.

Example - Old Age

• In the example, "Enter your old age" takes age as a string, stored as "Old Age".
• New age calculation requires converting input to an integer.

Error Handling in Calculations

• Type error occurs when mixing strings and integers.
• Convert "Old Age" to an integer using int() for math operations.

Additional Conversions

• Use float() for floating-point numbers.
• Use str() to convert to a string for printing.
• Use bool() to convert to a bool variable.

Python Program Example - Summing Numbers

• Input: Receive two numbers from the user.
• Convert: Change from string to integer.
• Print: Print the resultant sum.

String Manipulation Operations

• .upper(): Converts the string to uppercase.
• .lower(): Converts strings to lowercase.
• Use: string.upper() or string.lower() on the declared variable.
• The original string is not modified.

.find() strings

• Finds a string within a string and returns the first index.
• If the string cannot be found, it returns -1.

String Replacement

• Replaces parts or the whole string.
• Can replace characters.

Keyword in

• Used for true/false checks.
• Checks for the existence of a substring in a string.

Arithmetic Operators

• + for addition.
• - for subtraction.
• * for multiplication.
• / for division.
• // for division to an integer.
• % for remainder.

Power Operators

• Using ** for number power.

Shortcuts

• Use operators and equal signs as shortcuts: +=, -=, *=, etc.

Order of Operations

• Standard operator precedence applies.
• Use parentheses to take priority over existing ordering.

Python Comments

• Used for not code - text documentation of code

Comparison Operators

• Used for true/false checks
• Compares for greater than, less than, equals, etc

Logical Operators

• Use for true/false conditionals, and, or, not.

If/Else Statements

• Use conditionals to perform tasks depending on the outcome of other tasks.

Colons

• Used for calling if statements
• Indentation to specify actions following the statement

If/Else examples

• Checks various scenarios such as age

Mini Project Notes - Calculator

• Used to calculate operations depending on the input of arguments
• Also performs the logic of error handling to ensure arguments are valid

Ranges

• Functions like defining the numbers 0 to 4
• Includes the starting values, but not the last values (0..4)

Loops (While)

• Use while statements to do an action until the arguments specified are false

For loops

• Loops through an object and its contents and performs an action once

Lists

• Use lists to store elements
• Lists have an index that starts at zero, such as 0, 1, 2, etc
• Elements do not need to be the same type

Negative Indexing

• Lists can be indexed in the negative: -1 refers to the last item in the list

List Operations

• Adding to the back = Appending
• Adding at the front = inserting at zero with .insert(
• Check contents exist with object in list and is a true/false statement
• Get the length with len(list) and print
• Make the lists clear with list.clear()

Break / Continue Statements

• Break commands stop a loop at an object
• Continue skips an object in an index

Tuples

• Tuples are immutable lists
• Cannot change the elements

Tuples Operation / Functions

• Can count specific elements: tuple.count()
• Can use indexing: tuples.index()

Sets

• Sets only support unique types
• Accessed out of order

Dictionaries

• Stores key-value pairs, for instance storing marks that matches subject
• To access an object type in the key: dictionary[the key]
• To add a new key use: dictionary[the key] = value

Functions

• Functions help to modularize code and perform tasks

Types of Functions

• Inbuild: int(), bool(), etc
• Module: Import math functions
• User-Defined - the programmer decides/creates them.

Function Example: add( , ) arguments

• def print_sum(first,second): is used to define two arguments Then use `print_sum(argument 1, argument 2 ) calls that function