26 lines
904 B
Python
26 lines
904 B
Python
"""
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Compound interest function with ``decimal.Decimal``
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"""
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def compound_interest(principal, rate, periods):
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return principal * ((1 + rate) ** periods - 1)
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def test(verbose=False):
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from decimal import Decimal, getcontext
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getcontext().prec = 8
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fixture = [(1000, Decimal('0.05'), 1, Decimal('50')),
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(1000, Decimal('0.10'), 5, Decimal('610.51')),
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(1000, Decimal('0.10'), 15, Decimal('3177.2482')),
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(1000, Decimal('0.06'), 5, Decimal('338.2256')),
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]
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for principal, rate, periods, future_value in fixture:
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computed = compound_interest(principal, rate, periods)
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if verbose:
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print('{!r}, {!r}, {!r} -> {!r}'.format(
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principal, rate, periods, computed))
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assert future_value == computed, '{!r} != {!r}'.format(future_value, computed)
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if __name__ == '__main__':
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test(True)
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