Calculating arithmetic mean one type of average in Python

Question

Is there a built-in or standard library method in Python to calculate the arithmetic mean  one type of average  of a list of numbers

User · Accepted Answer

I am not aware of anything in the standard library. However, you could use something like:

def mean(numbers):
    return float(sum(numbers)) / max(len(numbers), 1)

>>> mean([1,2,3,4])
2.5
>>> mean([])
0.0

In numpy, there's numpy.mean().

User · Answer

Use scipy   import scipy  a  1 2 4   print scipy mean a

User · Answer

If you re using python  gt   3 8  you can use the fmean function introduced in the statistics module which is part of the standard library   gt  gt  gt  from statistics import fmean  gt  gt  gt  fmean  0  1  2  3   1 5  It s faster than the statistics mean function  but it converts its data points to float beforehand  so it can be less accurate in some specific cases  You can see its implementation here

User · Answer

Others already posted very good answers  but some people might still be looking for a classic way to find Mean avg   so here I post this  code tested in Python 3 6    def meanmanual listt    mean   0 lsum   0 lenoflist   len listt   for i in listt      lsum    i  mean   lsum   lenoflist return float mean   a    1  2  3  4  5  6  meanmanual a   Answer  3 5

User · Answer

def avg l          uses floating-point division         return sum l    float len l     Examples   l1    3 5 14 2 5 36 4 3  l2    0 0 0   print avg l1     9 0 print avg l2     0 0

User · Answer

def list mean nums       sumof   0     num of   len nums      mean   0     for i in nums          sumof    i     mean   sumof   num of     return float mean

User · Answer

The proper answer to your question is to use statistics mean  But for fun  here is a version of mean that does not use the len   function  so it  like statistics mean  can be used on generators  which do not support len     from functools import reduce from operator import truediv def ave seq       return truediv  reduce lambda a  b   a 0    b 1   b 0                                enumerate seq  start 1                                0  0

User · Answer

I always supposed avg is omitted from the builtins stdlib because it is as simple as  sum L  len L    L is some list   and any caveats would be addressed in caller code for local usage already   Notable caveats    non-float result  in python2  9 4 is 2  to resolve  use float sum L   len L  or from   future   import division division by zero  the list may be empty  to resolve   if not L      raise WhateverYouWantError  foo   avg   float sum L   len L

User · Answer

from statistics import mean avarage mean your list    for example  from statistics import mean  my list  5 2 3 2  avarage mean my list  print avarage    and result is  3 0

User · Answer

Instead of casting to float you can do following  def mean nums       return sum nums  0 0    len nums    or using lambda  mean   lambda nums  sum nums  0 0    len nums    UPDATES  2019-12-15  Python 3 8 added function fmean to statistics module  Which is faster and always returns float      Convert data to floats and compute the arithmetic mean       This runs faster than the mean   function and it always returns a   float  The data may be a sequence or iterable  If the input dataset is   empty  raises a StatisticsError       fmean  3 5  4 0  5 25        4 25       New in version 3 8

User · Answer

NumPy has a numpy mean which is an arithmetic mean  Usage is as simple as this    gt  gt  gt  import numpy  gt  gt  gt  a    1  2  4   gt  gt  gt  numpy mean a  2 3333333333333335

User · Answer

Use statistics mean   import statistics print statistics mean  1 2 4      2 3333333333333335   It s available since Python 3 4  For 3 1-3 3 users  an old version of the module is available on PyPI under the name stats  Just change statistics to stats

User · Answer

You don t even need numpy or scipy      gt  gt  gt  a    1  2  3  4  5  6   gt  gt  gt  print sum a    len a   3

[python] Calculating arithmetic mean (one type of average) in Python

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