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dmtucker/interest.py

Created April 25, 2020 03:46
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interest.py
import math
def apy(apr, periods=12):
return (((apr / periods) + 1) ** periods) - 1
def apr(apy, periods=12):
return (((apy + 1) ** (1 / periods)) - 1) * periods
apr_before = 0.12
apr_after = apr(apy=apy(apr=apr_before))
assert apr_after == apr_before, (apr_before, apr_after)
apy_before = 0.12
apy_after = apy(apr=apr(apy=apy_before))
assert apy_after == apy_before, (apy_before, apy_after)
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