Programming Fundamentals: Functions, Booleans, Loops

Posted on Dec 12, 2024 in Computers

Programming Fundamentals

Functions

Functions are a group of instructions that can be grouped together and referred to as a whole. They are small algorithms inside of a big algorithm, have inputs, and produce outputs (a set of instructions).

Format: function name (argument1, argument 2)

Example: print('hello world!')

Functions are a group of instructions that can be grouped together and referred to as a whole. They can have inputs and can produce/return outputs.

• Value-returning functions produce or return some output (something new).
• Example: user_name = input ('enter name: ')
• Void functions don’t return anything (subroutines).
• Example: print ('hello')

Defining a function:

def function_name (arg1: type1, arg 2: type 2...) -> return_type:

    instructions that use arguments

    return something

Void Functions

Void functions have no return statement; print is used instead.

def greeting(name: str) -> None:

    print(f'Hello {name}')

user_name = input('enter your name: ')

greeting(user_name)

Value-Returning Functions

Value-returning functions have a return statement at the end, making them value-returning.

def add_two_integers(x: int, y: int) -> int:

    the_sum = x + y

    return the_sum

sum = add_two_integers(2, 3)

print(sum)

Local and Global Variables

• Local variables are defined inside a function and are only accessible by that function.
• Global variables are defined in the main program and are accessible everywhere.

def add_2_numbers (x: float, y: float) -> none:

    sum = x + y <- local variable

    print (sum) <- function body

add_2_numbers (2.1, 3.8) <- arguments

Booleans

Booleans represent truth or false values.

Data Types

• int = integers
• float = real numbers
• str = text

Operators

• * = multiplication
• / = division
• // = integer division (6 // 4 = 1)
• % = remainder/mod (6 % 4 = 2)
• ** = exponent (2 ** 3 = 8)
• != (not equal)
• == (equal)

Logical Operators

• and – True if BOTH operands are true – (3 > 2) and (0 == 1) means false
• or – True if EITHER operand is true – (3 > 2) or (0 == 1) means true
• not – Inversion from true to false or false to true – not true means false

Decisions

If-Else Statements

Run a set of statements if a condition is true, and another set otherwise.

if temperature < 40:

    print("A little cold, isn't it?")

else:

    print("Nice weather we're having")

If-Elif-Else Statements

Test which of a set of conditions is true, and run the corresponding set of statements.

if temperature > 40:

    print('high fever')

elif temperature >= 37:

    print('fever')

else:

    print('normal')

Loops

Condition-Controlled Loops

Repeat an operation as long as some condition is TRUE.

five_was_found = False

while not five_was_found:

    rnd_number = randint(0, 10)

    print(rnd_number)

    five_was_found = rnd_number == 5

print('5 was found!')

Count-Controlled Loops

Repeat an operation a specified number of times.

iteration_number = 0

# loop 5 times

while iteration_number < 5:

    iteration_number += 1

    print(f'iteration number: {iteration_number}')

print('done')

Infinite Loops

Occur when the condition cannot be false, which can happen due to logic errors in the condition or if variables are not modified properly.

range(5) = [0, 1, 2, 3, 4]

range(5, 0, -1) = [5, 4, 3, 2, 1]

Example Functions

def compute_HRV(interval1: float, interval2: float, interval3: float) -> float:

def temperature_is_fever(temperature: float, site: str) -> bool:

def has_fever() -> bool:

def has_nausea() -> bool:

def has_low_HRV() -> bool:

def has_high_cortisol() -> bool:

def main() -> None:

main()