Week 1: Conditionals

Conditionals

Ability to ask questions and answer those questions, in order to decide which line of code will be executed.

• To write conditional statements in Python, we can use if statement.
• The elif statement, ask a question, taking into account whether or not a previous question had a true or false answer.
• The else statement, used when the all the other options has bee exhausted and only logical answer is the last one. So, we don’t need to compare anything for it, because it’s the only answer left. It’s catch all statement, if everything else isn’t proved right, let’s assume this is the answer.

Some symbols used in Python, are:

Not better design (See compare.py)

A better designed program:

The final design:

• In the first version, program goes through all the code despite finding the correction answer earlier.
• In the second iteration, program will immediately terminate as it gets its answer.

Boolean Expression

A question that gives Yes or No answer, or simply True or False answer.

OR Returns True if at least one operand is True; it only returns False if both operands are false.

AND Returns True if both operands are true; otherwise, it returns False. It’s uses short-circuit evaluation, meaning if the first operand is false, the second is not evaluated.

Python Operators

match…case Statement

Provides structural pattern matching as a more readable and powerful alternative to if-elif-else chains. It evaluates an expression against successive patterns and executes the corresponding code block for the first match.

match name:
    case 'Harry':
        print('Gryffindor')
    case 'Hermione':
        print('Gryffindor')
    case 'Ron':
        print('Gryffindor')
    case 'Draco':
        print('Slytherin')
    case _: # Handle edge cases
        print('Who?')

More legible or better version:

match name:
  case 'Harry' | 'Hermione' | 'Ron':
    print('Gryffindor')
  case 'Draco':
    print('Slytherin')
  case _:
    print('Who?')