Control logic

Hamish Gibbs

Tutorial #1: Conditional logic

• Conditional execution
• Core concepts:

  • Booleans (True, False)

    x = 5 == 5

  • Conditional execution

    if x > 0 :
        print('x is positive')

  • Catching exceptions

    try:
        # Some code that throws an error
    except:
        # A useful error message

Conditional logic: R to Python

• The concept is the same, the Python syntax is simpler.
  • In Python, pay attention to your indentation!

R

if (x > 0) {
    print('x is positive')
}

Python

if x > 0 :
    print('x is positive')

Tutorial #2: Iteration

• Iteration
• Core concepts:

  • Indefinite iteration (while)

    while x < 10:
        # Do something with x

  • Definite iteration (for)

    for x in range(10):
        print(x)

Iteration: R to Python

• Just like if statements, the R concept is the same, the Python syntax is simpler.

R

for (x in 1:3) {
    print(x)
}

Python

for x in [1, 2, 3]:
    print(x)

List comprehension

• Unique to Python: one-line iteration for lists.
  • Iterate over a list:

  y = [x for x in [1, 2, 3]]

  • Manipulate each element of a list:

  [x + 3 for x in y]

Tutorial #3: Iteration

• More control flow tools §4.1-4.6
• Core concepts:

  • The range() function

    range(3)

  • Other control statements (break, continue, pass)

  • match statements

    match x:
        case 0:
            print("x is 0")
        case _:
            print(f"x is anything else!")

Tutorial #3: Iteration

• Note: §4.6 mentions functions (def) which we will work with tomorrow!