Exercise 5: Merge Two Dictionaries by Hand — Possible Solution
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defaults = {"theme": "dark", "font_size": 12, "autosave": True}
overrides = {"font_size": 14, "language": "en"}

merged = {}

# First, copy every default in
default_keys = list(defaults.keys())
index = 0
while index < len(default_keys):
    key = default_keys[index]
    merged[key] = defaults[key]
    index += 1

# Then apply overrides on top — these win on any shared key
override_keys = list(overrides.keys())
index = 0
while index < len(override_keys):
    key = override_keys[index]
    merged[key] = overrides[key]
    index += 1

print(merged)

Output:
{'theme': 'dark', 'font_size': 14, 'autosave': True, 'language': 'en'}

WHY THIS WORKS AS AN ANSWER
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A while loop can't walk a dictionary directly the way a for loop can
("for key in some_dict") — it needs something with a length and index
access. Converting the keys to a list first, list(defaults.keys()),
gives the while loop something concrete to count through.

Copying defaults first and overrides second is what makes overrides
"win" on font_size: merged["font_size"] gets set to 12 by the first
loop, then overwritten to 14 by the second loop, since dictionary
assignment always replaces an existing key's value rather than adding
a duplicate. Reversing the order of the two loops would make defaults
win instead — worth trying deliberately to see the difference.