The list(itertools.product(a,b)) will use element in A.To make full list as the element, you could use nested list,like this:
list(itertools.product([tuple(a)], b)
Result:
[(('apple', 'mango', 'pear'), 'ripe'), (('apple', 'mango', 'pear'), 'raw'), (('apple', 'mango', 'pear'), 'rotten')]
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