Conditionals

The Password Checker was the first program you wrote that made a decision — read a password, weigh it, answer accordingly. That fork is a conditional — how programs stop being recordings and respond.

One question, two paths

password = input("Choose a password: ")
if len(password) >= 8:
    print("Long enough.")
else:
    print("Too short — aim for 8 or more.")

if asks a yes-or-no question: yes runs the first block, no runs the else block. Exactly one of the two paths ever happens.

More than two paths

elif — “else if” — chains more questions, checked top to bottom:

if len(password) >= 12:
    print("Strong.")
elif len(password) >= 8:
    print("Acceptable.")
else:
    print("Too short.")

Order matters: Python takes the first yes and skips the rest.

The operators that ask the questions

Comparisons produce the yes or no: ==, !=, <, >, <=, >=. Booleans combine answers — and (both), or (either), not (flip). The classic trap: = assigns, == compares — see Spot the Bug.

Questions inside questions

Checks can nest — ask a second question only if the first passes:

flowchart TD
    A{8 or more characters?} -- no --> R[Reject]
    A -- yes --> B{Contains a digit?}
    B -- no --> R
    B -- yes --> OK[Accept]

Nesting is easy to overgrow — three deep and squinting, flatten with and. Then Conditionals Practice makes the moves automatic.

Curriculum connection

C1.5

identify and explain situations in which conditional and repeating structures are required

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C2.3

write programs that include single and nested conditional statements

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C2.5

write programs that include the use of Boolean operators, comparison operators, text operators, and arithmetic operators

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