Python for Beginners - Learn Python in 1 Hour

This tutorial covers everything needed to start programming in Python, ideal for data science, machine learning, or web development. No prior knowledge of Python or programming is required as the course starts from scratch. Mosh Hamadani will guide you through the process; he has taught millions how to code.

Python is a multi-purpose programming language suitable for various tasks. It excels in machine learning and AI, being the top choice for data science projects. In web development, frameworks like Django enable building robust websites; notable examples include YouTube, Instagram, Spotify, Dropbox, and Pinterest. Additionally, Python enhances productivity through automation by handling repetitive tasks efficiently.

Setting Up Python and PyCharm To start programming in Python, first download the latest version from python.org. Ensure to check 'Add Python to PATH' during installation on Windows for seamless setup. Next, install a code editor like PyCharm; opt for the free Community Edition available at jetbrains.com/pycharm. Follow through with basic configuration steps upon opening it.

Creating Your First Python Program In PyCharm, create a new project named 'hello world'. Inside this project, add a new file called app.py and write your first line of code: print('Hello World'). This command uses the built-in print function to display text output in the terminal window when executed via Run menu or shortcut keys.

Understanding Variables in Python Variables are used to temporarily store data in a computer's memory, such as the price of a product or someone's personal information. To declare a variable, type its name followed by an equal sign and then the value (e.g., age = 20). This assigns the number 20 to 'age' which can be printed without quotes for numerical output. Variables can also hold decimal numbers, strings with underscores separating words for readability (e.g., first_name), and boolean values like True or False using proper case sensitivity.

Practical Exercise: Hospital Check-In Program To practice declaring variables, imagine writing a program for checking in patients at a hospital. For example: John Smith is 20 years old and is marked as new patient; you would create variables like `name`, `age`, and `is_new_patient` to store this information accordingly.

In this tutorial, we learn how to receive input from the user using Python's built-in 'input' function. By placing a prompt string inside the parentheses of 'input', such as "What is your name? ", and running the program, it displays this message and waits for user input. The entered value can be stored in a variable; for example, storing it in 'name'. We then use string concatenation with the print function to display a greeting that includes their name.

Understanding Type Conversion in Python In Python, there are three primary data types: numbers, strings, and booleans. Sometimes it's necessary to convert a variable's value from one type to another. For example, using the input function returns a string even if you enter a number; thus converting this string into an integer is essential for arithmetic operations like calculating age by subtracting birth year from the current year.

Practical Application of Type Conversion Functions Python provides built-in functions such as int(), float(), bool(), and str() for type conversion. These functions help ensure that variables are correctly typed before performing operations on them. In practice exercises like creating calculators or combining different numeric inputs (integers and floats), these conversions prevent errors related to incompatible data types.

Understanding String Methods in Python In Python, strings are objects with various methods that allow manipulation and querying. For example, the 'upper' method converts a string to uppercase without altering the original string; it returns a new one instead. Similarly, 'lower' changes all characters to lowercase while 'find' locates the index of specific characters or sequences within a string. The immutability of strings means any modification results in creating an entirely new object.

Using Replace Method and In Operator for Strings The replace method allows substitution within strings but does not alter the original content due to their immutable nature—it generates a new modified version instead. To check if certain substrings exist within another string efficiently, use either find (which gives you an index) or more intuitively through Python's readable syntax using ‘in’ operator which returns boolean values indicating presence.

Python includes arithmetic operators similar to those in mathematics, such as addition (+), subtraction (-), multiplication (*), and division (/). Division can be performed using a single slash for floating-point results or double slashes for integer results. The modulus operator (%) returns the remainder of a division, while the exponentiation operator (**) raises numbers to a power. Augmented assignment operators like += allow more concise code by combining operations with assignments.

When declaring a variable x set to 10 plus 3 times 2, the result is determined by operator precedence. Multiplication and division have higher precedence than addition and subtraction, so they are evaluated first. Therefore, in this expression: 3 times 2 equals 6; then add it to the initial value of ten resulting in sixteen (16). In Python, as with math generally speaking - you can alter order using parentheses for different outcomes.

Comparison operators are used to compare values and produce boolean expressions. For example, '3 > 2' evaluates to true because three is greater than two. Key comparison operators include: greater than (>), less than (<), equal (==), not equal (!=). These operators are essential for evaluating conditions in real-world Python programs.

Logical operators are used to build complex rules and conditions. For example, using the 'and' operator checks if both expressions return true; for instance, checking if a price is between 10 and 30 dollars returns true when it meets this condition. The 'or' operator requires at least one expression to be true; changing the price to 5 still results in a valid condition because it's less than 30. Lastly, the 'not' operator inverses any given value: applying it on an expression that evaluates as false will turn it into true.

Making Decisions with If Statements in Python In this tutorial, we explore how to use if statements in Python for decision-making. By declaring a variable like temperature and using comparison operators within an if statement, different messages can be printed based on the value of that variable. Indentation is crucial as it defines blocks of code executed when conditions are met; unlike C-based languages which use curly braces.

Using Multiple Conditions and Else Blocks We learn to handle multiple conditions by employing elif (else-if) statements alongside our initial condition checks. This allows us to print specific messages depending on various ranges of values for the temperature variable. The else block captures any scenario not covered by previous conditions, ensuring comprehensive control flow management.

Building a Weight Converter Program Create a weight converter program that asks for the user's weight and whether it is in kilograms or pounds. Use input functions to get these values, storing them in variables 'weight' and 'unit'. Implement an if statement to check if the unit is kilograms ('k') or pounds ('l'), converting accordingly using string methods like upper() for case insensitivity. Convert weights by dividing by 0.45 (for kg to lbs) or multiplying by 0.45 (for lbs to kg), then print the results.

Handling Errors with Type Conversion When running into errors such as trying to multiply strings with floats, remember that Python's input function returns strings which need conversion before arithmetic operations can be performed on them—use int() or float(). Similarly, when concatenating numbers within strings during output statements, convert those numbers back into strings using str(). These conversions prevent type-related runtime errors ensuring smooth execution of your code.

Introduction to While Loops in Python While loops are used in Python to repeat a block of code multiple times. Instead of writing repetitive print statements, we can use while loops for tasks like printing numbers from 1 to 5 or even up to one million by setting an initial variable and defining a condition.

Implementing the Loop with Increment Declare a variable (e.g., i) and set it initially (e.g., i = 1). Use 'while' followed by a condition (i <= 5), then write the code inside this block that will execute as long as the condition is true. Remember to increment your variable within the loop; otherwise, it will run indefinitely.

Practical Example: Printing Numbers Efficiently 'While' evaluates conditions iteratively until they become false. For instance, starting at i=1 and ending when i > 5 prints numbers from one through five efficiently without manually coding each line.

Enhancing Readability with Underscores 'Underscore separators make large numbers more readable.' Changing our upper limit from five thousand underscores makes reading easier but doesn't affect functionality—demonstrating flexibility in handling larger ranges effortlessly using while loops instead of extensive manual entries.

Introduction to Lists in Python In Python, lists are used to represent a collection of objects such as numbers or names. A list is declared using square brackets with elements separated by commas. For example, `names = ['john', 'bob', 'marsh', 'sam', 'mary']`. Individual elements can be accessed via their index (starting from 0) and negative indices allow access from the end of the list.

Manipulating List Elements Python allows changing an element at a specific index directly by assigning it a new value (`names[0] = ‘jon’`). Slicing enables selecting ranges within lists; for instance, `names[0:3]` returns the first three items without altering the original list.

Lists in Python are objects, similar to real-world items like mobile phones or bicycles. They have various methods for adding and removing elements. For example, the append method adds an element at the end of a list, while insert allows placing an item at any position by specifying its index. The remove method deletes specified items from a list; clear removes all elements entirely. To check if an item exists within a list, use the 'in' operator which returns boolean values.

Iterating Over a List with For Loops When writing Python programs, there are times you want to iterate over a list and access each item individually. Declaring a list of numbers one through five, printing the entire list shows it in square bracket notation. To print each item on separate lines, use a for loop by declaring an iteration variable (e.g., 'item') that holds values sequentially from the list during iterations.

Using While Loops for Iteration The same result can be achieved using while loops but requires more code. Start by declaring an index variable outside the loop and set it to zero; then use len() function to determine how many items are in the list. Inside the while loop conditionally check if this index is less than length of lists' elements count; incrementing after accessing element at current index position.

Comparing For Loop vs While Loop Efficiency For loops offer shorter and easier-to-understand implementations compared to while loops when iterating over lists in Python. With for loops, there's no need for explicit indexing or calling functions like len(), making them preferable due their simplicity and readability.

The range function in Python generates a sequence of numbers. By passing a single value, it creates numbers from 0 up to but not including that value. To see these values, iterate over the range object using a for loop. You can also specify start and end points or include an optional step parameter to control increments.

Understanding Tuples in Python Tuples are similar to lists but immutable, meaning they cannot be changed once created. Defined using parentheses instead of square brackets, attempting to reassign elements results in an error. Unlike lists, tuples lack methods like append or remove; they only have count and index for counting occurrences and finding the first occurrence's index.

Practical Use Cases for Tuples While most often you would use lists due to their flexibility, tuples ensure that a sequence of objects remains unchanged throughout your program. This immutability can prevent accidental modifications by yourself or others.

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