What s the function like sum but for multiplication product

Question

Python s sum   function returns the sum of numbers in an iterable   sum  3 4 5      3   4   5    12   I m looking for the function that returns the product instead   somelib somefunc  3 4 5      3   4   5    60   I m pretty sure such a function exists  but I can t find it

User · Answer

There isn t one built in  but it s simple to roll your own  as demonstrated here   import operator def prod factors       return reduce operator mul  factors  1    See answers to this question     Which Python module is suitable for data manipulation in a list

User · Answer

Use this  def prod iterable       p   1     for n in iterable          p    n     return p   Since there s no built-in prod function

User · Answer

There s a prod   in numpy that does what you re asking for

User · Answer

Perhaps not a  builtin   but I consider it builtin  anyways just use numpy  import numpy  prod sum   numpy prod some list

User · Answer

Update  In Python 3 8  the prod function was added to the math module   See  math prod    Older info  Python 3 7 and prior The function you re looking for would be called prod   or product   but Python doesn t have that function   So  you need to write your own  which is easy   Pronouncement on prod   Yes  that s right   Guido rejected the idea for a built-in prod   function because he thought it was rarely needed  Alternative with reduce   As you suggested  it is not hard to make your own using reduce   and operator mul    from functools import reduce    Required in Python 3 import operator def prod iterable       return reduce operator mul  iterable  1    gt  gt  gt  prod range 1  5   24  Note  in Python 3  the reduce   function was moved to the functools module  Specific case  Factorials As a side note  the primary motivating use case for prod   is to compute factorials   We already have support for that in the math module   gt  gt  gt  import math   gt  gt  gt  math factorial 10  3628800  Alternative with logarithms If your data consists of floats  you can compute a product using sum   with exponents and logarithms   gt  gt  gt  from math import log  exp   gt  gt  gt  data    1 2  1 5  2 5  0 9  14 2  3 8   gt  gt  gt  exp sum map log  data    218 53799999999993   gt  gt  gt  1 2   1 5   2 5   0 9   14 2   3 8 218 53799999999998  Note  the use of log   requires that all the inputs are positive

User · Answer

I prefer the answers a and b above using functools reduce   and the answer using numpy prod    but here is yet another solution using itertools accumulate     import itertools import operator prod   list itertools accumulate  3  4  5   operator mul   -1

User · Answer

Actually  Guido vetoed the idea  http   bugs python org issue1093  But  as noted in that issue  you can make one pretty easily   from functools import reduce   Valid in Python 2 6   required in Python 3 import operator  reduce operator mul   3  4  5   1

User · Answer

Numeric product      or   reduce lambda x y x y  3 4 5

[python] What's the function like sum() but for multiplication? product()?

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