Exercise 2: A Fourth Extracted Condition — Possible Solution
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THE ADDED CONDITION
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    def is_eligible_bad(user):
        if (user['age'] >= 18 and user['country'] == 'US'
                and user['verified'] and user['has_valid_payment_method']):
            return True
        return False

    def is_eligible_good(user):
        is_adult = user['age'] >= 18
        is_us_resident = user['country'] == 'US'
        is_verified = user['verified']
        has_valid_payment_method = user['has_valid_payment_method']
        return is_adult and is_us_resident and is_verified and has_valid_payment_method

A user who fails ONLY the new payment condition:
    {'age': 25, 'country': 'US', 'verified': True, 'has_valid_payment_method': False}

RESULTS
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    BAD version - only tells you the final answer:
      is_eligible_bad: False

    GOOD version - each condition independently inspectable:
      is_adult: True
      is_us_resident: True
      is_verified: True
      has_valid_payment_method: False
      -> immediately clear the ONLY failing condition is has_valid_payment_method

    Full agreement check across 5 cases (the original 4 plus this one):
      bad=True,  good=True,  match=True
      bad=False, good=False, match=True
      bad=False, good=False, match=True
      bad=False, good=False, match=True
      bad=False, good=False, match=True
    ALL match: True

Both versions still agree on every case after the fourth condition is
added, and the extracted version still isolates exactly which single
condition caused a rejection - now correctly pointing at payment
method instead of age, country, or verification status.

WHY THIS WORKS AS AN ANSWER
------------------------------
The chapter's own debugging finding for the original three conditions
- that Extract Variable makes the specific failing condition visible -
holds without modification as a fourth condition is added. The benefit
doesn't degrade as the expression grows; if anything it becomes more
valuable, since a four-way compound boolean is harder to mentally
re-evaluate by hand than a three-way one, and the bad version still
offers no way to do it at all.