Untitled Quiz

Python Basics

• Python is a dynamic language, meaning variable types are determined at runtime, offering flexibility in assigning various data types to variables.
• It's strongly typed, enforcing strict type rules. Implicit conversions (e.g., combining strings and integers) are prevented, which may generate errors.
• Control flow structures include conditional statements (e.g., if, elif, else) and loops (e.g., for, while) for decision-making and repetitive operations respectively.
• Python supports exception handling (try, except, finally) and control flow statements (break, continue, pass) for managing code execution within loops and blocks.

Pass By Value vs. Returning a Value

• In the first example, the function modifies a local copy of the variable, not the original, and hence output is 1.
• In the second example, the function returns a value, and the variable will hold that returned value. In that case, the output is 2.

Functions

• set(): Creates a set from a sequence of elements, removing duplicates.
• map(): Applies a function to each item in an iterable. (Often converted to a list)
• split(): Splits a string into substrings(based on whitespace by default)
• len(): Returns the number of elements in a collection.

More Functions

• sum(): Calculates the sum of all elements in a collection.
• add(): Adds an element to a set; if the element exists, the set remains unchanged.

More Functions (Continued)

• discard(): Removes an element from a set if it exists; does nothing if the element doesn't exist.
• The remove() method, unlike discard(), raises an error if the element is not present.

append()

• Adds an element to the end of a list.
• Modifies the original list directly.
• Doesn't return a new list.

Lambda Functions

• Lambda functions are small, anonymous functions.
• Useful when a small function is needed temporarily.
• Usually combined with functions like map(), filter(), and sorted().
• Syntax: lambda arguments: expression

Lambda and Built-in functions

• In a map operation, lambda functions are applied to each item in a list to perform operations such as squaring each number.
• The filter operation works with lambda functions to filter items from a list based on a provided condition such as getting only even numbers.
• sorted uses lambda to sort items such as lists of tuples by a specific component.
• Sorting a list of dictionaries can be done using the sorted function in conjunction with a lambda function.

range()

• Used in loops to iterate over a sequence of numbers, specifying the number of iterations or to access elements by index.
• Syntaxes:
  • range(stop): Generates numbers from 0 to stop-1.
  • range(start, stop): Generates numbers from start to stop-1.
  • range(start, stop, step): Generates numbers from start to stop-1 with increments of step.

Scope of Variables in Python

• Python has four built-in scopes: Built-in, Global, Enclosing (Nonlocal), and Local (LEGB).
  • Variables within functions have local scope and are only accessible within the function itself.
• Enclosing functions(nested functions) have access to variables in enclosing scope.
• Global variables are declared outside functions and accessible throughout the entire program.

Recursion

• Recursion occurs when a function calls itself, directly or indirectly, as part of its execution,
• Every recursive function needs a base case to stop the recursion and prevent infinite loops.
• Recursive cases are where the function calls itself with a modified argument gradually moving toward the base case.

Example: Factorial Calculation

• Factorial of a non-negative integer n, denoted by n!, is the product of all positive integers less than or equal to n.
• n! = n * (n-1) * (n-2)... * 1

Example: factorial Function

• This function calculates the factorial of a given non-negative number using recursion and the base case(n==1).

Valid or Invalid Code Snippets

• Demonstrates correct and incorrect ways to utilize Python features like classes, methods, and exception handling to avoid common errors and misunderstandings about them.

String Methods

• String concatenation (+) combines two strings into one.
• String repetition (*) repeats strings multiple times
• String slicing ([start:end]) fetches a substring
• String splitting (.split()) breaks a string into a list of substrings.
• String joining ('.join') joins list of strings into one string
• String replacing (replace()) replaces a substring of another.

String Methods(continued)

• String case functions (lower(), upper(), capitalize(), title()): Modifies lowercase/uppercase characters.
• Strip whitespace function (strip(), rstrip, lstrip): removes leading and trailing spaces/characters
• String methods like find() are for searching for a substring within a string
• in keyword: Checks for a string within another string
• String formatting: Inserts variables into strings either by using .format or f-strings

String Slicing Use Cases

• Extract substrings from a given range of indices
• Reverse a string
• Handling out-of-bounds indices
• Immutability in string slicing: Slicing creates a separate copy of strings

Looping Statements (General Points)

• Python offers two primary looping constructs: for and while.
• Use for when the loop count is known, and use while when it's not.

Exceptions (General Points)

• Exceptions are errors that occur during program execution.
• try...except blocks are used to handle potential exceptions gracefully, preventing crashes.

File I/O (General Points)

• The open() function is used to create a file object for reading, writing, or appending data to a file.
• File handling modes like 'r' (read), 'w' (write), 'a' (append), 'r+' (read and write), etc are used when opening file.
• The close() method is crucial to release the file resources.
• Function like read(), readline(), readlines() can be used to read data from a file line by line