Algorithms, Pseudocode and Flowcharts

Topic 1

• A problem is a state of difficulty that requires a resolution.
• An algorithm is a set of precise instructions that define the tasks to be performed and their order.
• Algorithms can be represented using pseudocode and flowcharts.

Steps to Develop a Program

• Define the problem clearly.
• Outline a solution to the problem.
• Develop this outline into a detailed algorithm.
• Test the algorithm to ensure its correctness.
• Code the algorithm in a specific programming language.
• Run the program on a computer.
• Document and maintain the program to ensure its continued functionality.

Pseudocode

• Pseudocode is formalized and abbreviated English resembling high-level computer languages.
• Keywords: START, END, IF, ELSEIF, PRINT, DISPLAY, SHOW, OUTPUT, PUT
• Examples of Repetition Keywords: FOR, WHILE/ENDWHILE, REPEAT/UNTIL, DO/WHILE/ENDWHILE

Flowcharts

• Flowcharts should generally be drawn from top to bottom.
• All boxes/shapes in a flowchart should be connected with arrows to indicate flow.
• Common Flowchart Symbols:
  • Terminal: Indicates the start or end of the flowchart.
  • Input/Output: Represents input or output operations.
  • Process: Denotes a calculation or processing step.
  • Decision: Represents a decision point (IF statements).
  • Predefined Process: Indicates a subroutine or function call.
  • On-page Connector: Connects different parts of the flowchart on the same page.
  • Flow: Shows the direction of the process.

Topic 2: Types of Operators

• Arithmetic Operators: +, -, *, /, %
• Comparison Operators: ==, !=, >, <, >=, <=
• Logical Operators: &&, ||, !
• Assignment Operators: =, +=, -=, *=, /=, %=
• Increment and Decrement Operators: ++, --
• Bitwise Operators: &, |, ^, ~, >>, <<

Relational Operators

• : Greater than

• =: Greater than or equal to

• <: Less than
• <=: Less than or equal to
• ==: Equal to
• !=: Not equal to

Logical Operators

• && (AND): Yields true if both expressions connected by the operator are true.
• || (OR): Yields true if either expression connected by the operator is true.
• ! (NOT): Reverses the value of an expression (true becomes false, and vice versa).

Types of Selection

• Simple Selection (simple IF)
• Simple Selection with NULL FALSE
• Combine Selection (combined IF)
• Nested Selection (Linear and Non-Linear)

Simple Selection

• Employs a direct IF statement to make decisions based on a condition.

Simple Selection with NULL FALSE

• May involve checking for undefined or missing values.

Combine Selection

• Uses logical operators to verify multiple conditions within a single IF statement.

Nested Selection

• It involves placing one IF statement inside another and can be linear (one inside another) or non-linear (multiple branches).
• In Linear Nested Selection, an incorrect condition will lead directly to another condition.
• Non-linear Nested Selection implyies other processes occur between the conditions selected..

Repetition

• For Loop
• While Loop
• Do While Loop ( Known as Post test loop)

Types of LOOP

• Pre-test loop
• Post-test loop (Used in C, C#, Java)

Repetition Structure

• Can be used to control execution of the loop with a loop control variable
• Loop control variable will increment or decrement each time a loop repeats
• Loop control variable must be initialized before entering loop

For Loop

• Typically used when the number of iterations is already known before execution.
• Often employed to iterate through a sequence, such as a list, tuple, string, or range.
• The loop control variable is managed automatically.

While Loop

• Used when the number of iterations is unknown at the start and depends on a condition.
• Will execute as long as the specified condition remains True.
• The loop control variable initialized, checked, and updated by the programmer.

Topic 3: What is Programming Language?

• A programming language provides a way to instruct a computer on what operations to execute.
• It provides a linguistic framework for describing computations.
• It serves as a notation system to describe computation in a machine-readable and human-readable manner.
• It's a tool to develop executable models within various problem domains.

Source Code

• Includes everything from variable initialization to conditional statements and print functions.

Syntax

• Correct syntax for if-else statements requires a colon after conditions and proper indentation.

Output

• Relies on the values of variables to deliver a final result.

Console

• Output is printed in this text box within an IDE or terminal.

Compared to

• PYTHON is Interpreting Language.

Difference Between Compiling and Interpreting

Comment in Python

• Use # for single-line comments.
• Use triple quotes (''' or """) for multi-line comments or docstrings.

Topic 4: Implementing PYTHON

• Important Data Types to Remember

Variable Declaration Guidelines

• Variable names must begin with a letter or an underscore.
• Variable names can only contain alphanumeric characters and underscores.
• Variable names should not be a reserved keyword.
• Variable names should be descriptive to indicate their purpose.

Order Precedence Rules

• Order of operations in Python (from highest to lowest precedence):
  • Parentheses ()
  • Power ** (exponentiation)
  • Multiplication *, Division /, Modulus %
  • Addition +, Subtraction -
  • Left to Right

Boolean Value

• Can be either YES or NO, or True or False

Decision Structures in Python with Examples

• 1. One-Way Decision (if): Executes a block of code if the condition is met.
• 2. Two-Way Decision (if-else): Executes one block if the condition is true, or else, another block if the condition is false.
• 3. Multiway Decision (if-elif-else): Executes one block of code from several available blocks according to multiple conditions.

Pass Statement

• A statement to leave it open for future work, where code will eventually go

Return Statement

• Will exit a function and pass an expression back to the caller, if it contains one.

Break Statement

• Exits a loop early before it finishes.

Continue Statement

• Skips the current time around the loop and will proceed to the next part of the iteration.

Explanation of range(start, stop, step)

• start: The beginning value of the sequence (inclusive).
• stop: The end value of the sequence (exclusive).
• step: The value between increments or decrements.

Using else Statement with While Loop

• Occurs if the while loop completes without hitting the break statement.

Chapter 7: Functions

• Functions are reusable code blocks to perform certain tasks.

Defining a Function

• Functions are created using the def keyword.

Arguments and Parameters

• Parameters in function definitions serve as placeholders for values that will be passed when the function is called.
• Arguments in function calls are the actual values or expressions passed to a function.

Pass by Reference and Pass by Value

• When passing immutable objects in function (like integers, strings, tuples) a copy is passed
• This does not affect the original object
• When passing mutable objects in a fuction (like lists, dict) the object is modified by the function
• This does affect the original object

Fruitful (Return Values) and Void (Non-fruitful) Functions

• Fruitful functions return a value when needed
• Void functions will perform an operation without returning a value explicitly

Built in Python Functions

• A helpful set of many functions.
• print(): Outputs messages or variables to the console.
• len(): Returns the length (number of items) of an object like a string, list, or tuple.
• input(): Reads input from the user via the console.
• type(): Returns the type of an object (e.g., int, str, list).
• int(): Converts a string or number to an integer.
• float():Converts a string or number to a floating-point number.
• str(): Converts an object into a string representation.
• list(): Creates a list from iterable objects like tuples or converts a string to a list.
• tuple(): Creates a tuple from iterable objects or converts a list to a tuple.
• dict(): Creates a dictionary or converts a sequence of key-value pairs into a dictionary.
• range(): Generates a sequence of numbers.
• sorted(): Returns a new sorted list from the elements of any iterable.
• sum(): Returns the sum of all elements in an iterable.
• max(): Returns the maximum element from an iterable or a series of arguments.
• min(): Returns the minimum element from an iterable or a series of arguments.
• abs(): Returns the absolute value of a number.
• all(): Returns True if all elements of an iterable are true (or if the iterable is empty).
• any(): Returns True if any element of an iterable is true. If the iterable is empty, it returns False.
• callable(): Checks if the object is callable (e.g., functions, methods).
• enumerate(): Returns an enumerate object that yields tuples containing a count (index) and the values obtained from iterating over a sequence.
• filter(): Constructs an iterator from elements of an iterable for which a function returns true.
• map(): Applies a function to all items in an input iterable.
• zip(): Returns an iterator of tuples, where the i-th tuple contains the i-th element from each of the input iterables.
• chr(): Returns the string representing a character whose Unicode code point is the integer.
• ord(): Returns the Unicode code point for a given character.
• round(): Rounds a floating-point number to a specified number of decimals or to the nearest integer.
• dir(): Returns a list of attributes and methods of any object (without the __ methods).
• eval(): Evaluates a string containing a Python expression.
• globals(): Returns the dictionary representing the current global symbol table.
• locals(): Returns the dictionary representing the current local symbol table.
• append(): Adds an element to the end of a list.
• pop(): Removes and returns the last element from a list, or removes and returns the element at a specified index.
• insert(): Inserts an element at a specified position in a list.
• index(): Returns the index of the first occurrence of a value in a list.

String Methods

Chapter (Stings Slicing)

• Strings in Python are indexed, meaning each character in the string has a position, starting from 0 for the first character
• Negative indices will count from the end of the string
• Slicing will extract a substring by selecting string[start:end:step]

The in Operator

• Checks if a value exists within an iterable (like strings, lists, tuples, etc.).

Tips to remember

• strings cannot be modified, create a new one

String Formatting

• String formatting will allow you to insert values into strings in a specific way.

Chapter 9: Lists and Tuples

• Lists can be indicated by [].
• Tuples can be indicated by ().

• Important to note is that immutable simply means unchangeable.

Built in List Functions

• append(): Adds an element to the end of the list.
• extend(): Extends a list by appending elements from an iterable.
• insert(): Inserts an element at a specified position.
• remove(): Removes the first occurrence of a value from the list.
• pop(): Removes and returns the last element from the list, or removes an element at a specified index.
• index(): Returns the index of the first occurrence of a value in the list.

Set Rules

1. Unordered
2. Mutable
3. Unique elements
4. Cannot contain 'lists'
5. Using "set()" can convert list to set

Sets

Dictionaries

• key-value pairs
• mutable
• unordered
• only unique keys
• keys are immutable

Dictionary Methods

• clear(): Removes all items from the dictionary.
• copy(): Returns a shallow copy of the dictionary.
• get(key[, d]): Returns the value for the key, or default d if key doesn't exist.
• items(): Returns a view of the dictionary's items as (key, value) pairs.
• keys(): Returns a view of the dictionary's keys.
• update(): Updates the dictionary with key/value pairs from another dictionary.
• values(): Returns a view of the dictionary's values.
• fromkeys(seq[, v]): Creates a new dictionary with keys from seq and values set to v.
• pop(key[, d]): Removes and returns the value associated with key, returns d as defaul, or does not return and gives an error.
• popitem(): Removes and returns an arbitrary (key, value) pair.

Chapter 11: File Handling

• OPENING FILE -> Connecting an external file with a program
• READING/WRITE FILE -> Adjusting and reading file data
• CLOSING FILE -> Disconnecting file

File Access Modes

Error Handling

• Syntax Errors (Compile-time Errors): Grammatical mistakes cause issues.
• Runtime Errors (Exceptions): Unexpected issues.
• Logical Errors: Mistakes in an algorithm causes errors in results.

try, except structure

• try: attempts a line of code
• except: if there is an error from the prior step, this line is run.
• there also exist names for specific errors such as ZeroDivisionError , NameError, IndentationError, IOError, EOFError

try finally structure

• if certain code must be run, it is run in the finally section whether there is an error or not

Logging

• Logging allows you to track certain events that are happening running softwares.
• The logging function is used to provide a simple set of functions for logging purposes.