Implication

Implication has the symbol of $⟹$. Implication means that $\neg P\vee P$. It is easier to think about this in Python code.

def implies(a, b):
    return (not a) or b

Or by using the phrase: If it rains ($P$) then I will need to bring my umbrella ($Q$).

• If it is not raining ($P$) and you don’t bring an umbrella ($Q$) then you are fine
• If it is not raining ($P$) and you brought an umbrella ($Q$) then it’s annoying but fine
• if it is raining ($P$) and you didn’t bring an umbrella ($Q$) then it’s not fine
• If it is raining ($P$) and you brought an umbrella ($Q$) it is fine

Essentially, you want a case where you do not get wet!

A use case for this is if we wanted to assert that if an admin exists they must have 2FA:

assert (not user.is_admin) or user.has_2fa  # admin ⇒ has 2FA