# Reduce with Python and Clojure

I was just playing around writing an annuity calculator function. Here is my first version:

def calculate_annuity(years, interest=0, addition_per_year=0, starting_amount=0):
result = []
running_total = starting_amount
for year in range(years+1):
result.append(running_total)
running_total = (running_total + addition_per_year) * (1 + interest)
return result


Here is a 2nd version, written using reduce instead of a loop:

def calculate_annuity2(years, interest=0, addition_per_year=0, starting_amount=0):
return reduce(lambda result,addition: result + [(result[-1] + addition) * (1 + interest)],


And here is a version in Clojure (basically a direct translation of the Python one:

(defn annuity [years interest addition_per_year init]
(reduce
#(conj %1 (* (+ (last %1) %2) (+ 1 interest)))
[starting_amount]

; Find investment returns by year for a $1000 investment at 7% interest ; for 10 years. (println (annuity 10 0.07 0 1000)) ; Find annuity value if contributing$1000 each month and starting with $7777 ; with 10% interest for 10 years. (println (annuity 10 0.10 1000 7777)) ; Find annuity value if contributing$1000 each month and starting with $777 ; with 10% interest for 10 years. (println (annuity 10 0.07 0 1000)) ; Test perpetuity annuity that pays out$6000 per year, given a \$100000