Algorithms, Pseudocode, Flowcharts & Python

• These are study notes on Algorithms, Pseudocode, Flowcharts, Structured Programming, Python, and more

Unit 1: Algorithms, Pseudocode, and Flowcharts

• Algorithm: Step-by-step instructions for problem-solving
• Pseudocode: A semi-formal way of writing algorithms in simple English
• Flowchart: A graphical representation of algorithms using symbols and arrows

Structured Programming

• Sequence: Straightforward steps
• Selection: Making decisions, exemplified by IF-THEN-ELSE
• Repetition: Looping, for example, DO WHILE

Steps to Developing a Program

• Define the problem
• Outline the solution
• Develop the algorithm
• Test the algorithm
• Code the algorithm
• Run the program
• Document and maintain the program

Unit 2: Introduction to Python

• Python: A versatile programming language

Interactive vs Script

• Interactive mode involves direct commands
• Script mode uses commands stored in a file

Variables

• Use meaningful names for variables
• Variable names can include letters, numbers, and underscores
• A variable name cannot start with a number or a reserved keyword

Keywords

• Keywords are reserved words in Python
• Examples of keywords are if, else, and for

Expressions and Statements

• Assignment statement example: x = 2
• Print statement example: print(x)
• Constants: Fixed values, such as numbers and strings
• Type Conversion functions: int(), float(), str()
• User Input: Achieved using the input() function
• Comments: Use # for single-line comments

Unit 3: Algorithm - Selection Structure

• Selection Structure: Used for decision-making in algorithms
• Relational Operators: <, >, ==, <=, >=, !=
• Logical Operators: && (AND), || (OR), ! (NOT)

IF Statements

• Simple IF statement: IF condition THEN action
• IF statement with ELSE: IF condition THEN action1 ELSE action2
• Combined IF statement: Using AND, OR
• Nested IF statements: IF statements within IF statements
• CASE OF Structure: Handles multiple conditions

Unit 4: Python - Selection Structure

• Comparison Operators: ==, !=, <, >, <=, >=
• One-Way Selection: Simple IF statements
• Two-Way Selection: IF-ELSE statements
• Multi-Way Selection: ELIF for multiple conditions
• Nested Decisions: IF statements inside other IF statements
• Errors can be handled gracefully using Try/Except

Unit 5: Algorithm - Repetition Structure

• Repetition Structure: Actions repeat until a condition is met
• Counter-Based Loops: Use a counter to control repetitions
• Sentinel-Based Loops: Employ a special value to end the loop
• DOWHILE Structure: Repeats while a condition remains true
• LOOP Statement: Loop with a counter from start to end

Unit 6: Python - Repetition Structure

• While Loop: Repeats as long as a condition is true
• For Loop: Iterates over a sequence like a list or range
• Break and Continue: Control loop flow
• Definite Loops: Have a known number of iterations
• Sentinel Loops: Have an unknown number of iterations, controlled by input

Unit 7: Python - Functions

• Functions: Reusable code blocks
• Defining Functions: Use the def keyword
• Calling Functions: Use the function name and arguments
• Void Functions: Have no return value
• Fruitful Functions: Return a value
• Parameters and Arguments: Inputs passed into functions

Unit 8: Python - File Processing

• File Handling: Includes opening, reading, writing, and closing files

File Modes

• r: Read mode
• w: Write mode (creates the file if it doesn't exist)
• a: Append mode (creates the file if it doesn't exist)
• File Handle: A variable used to manipulate the file
• Reading and Writing: Loops are used to process file lines

Python Programming: Strings and Data Collections

• Strings: A sequence of characters enclosed in quotes ("Hello" or 'Hello')
• Concatenation of strings is done using +
• Strings containing numbers are still strings; use int() to convert them to integers
• Reading and Converting: Data is read as strings and then converted as needed
• Use input() to read data and convert using int() or other conversion functions

Indexing and Length

• Access characters in a string using indexing, which starts at 0
• Use len() to get the length of a string
• Looping Through Strings: Iterate through each character using while or for loops

String Operations

• Slicing: Extract substrings using [start:end]
• Searching: Use find() to locate substrings
• Replacing: Use replace() to replace substrings
• Stripping: Remove whitespace with strip(), lstrip(), rstrip()
• Splitting: Use split() to divide strings based on a delimiter

String Library Functions

• String functions like lower(), upper(), capitalize(), etc., are built-in
• Use dir(string) to list all available string functions

Data Collections

• Lists: Ordered, changeable, and allow duplicates; defined using square brackets
• Operations on Lists: Create (new_list = [] or new_list = list(range(10))), Add (append(), insert()), Access (using indexing and slicing), Process (looping), Functions (len(), min(), max(), sum(), remove(), pop())
• Tuples: Ordered, unchangeable, and allow duplicates; defined using parentheses
• Sets: Unordered, unchangeable, and do not allow duplicates; defined using curly braces

Dictionaries

• Dictionaries: Ordered, changeable, no duplicates
• Store data in key-value pairs example: mydict = {"name": "Adam", "role": "chef"}
• Operations: Access (dict.get('key')), Functions (clear(), copy(), fromkeys(), items(), keys(), pop(), popitem(), update(), values())
• JSON: json.dump() to write and json.load() to read from JSON files