How to find average value of a list in python [duplicate]

This question already has an answer here:


number of values in a list greater than a certain number

6 answers




I want to return a function which gives the average of all the marks which are 50 or more. When I run my code, it always returns an empty list. Here is what I have tried:

def get_pass_average(marks):
average = []
for count in marks:
if count >= 50:
average = sum(count) / len(count)
return round(average,2)

def test_get_pass_average():
list1 = [50, 83, 26, 65, 92, 29, 77, 64]
print('%.2f' % (get_pass_average(list1)))


Please helps me to figure out the problems in my code, and the output should be 71.83. Many thanks.

In addition to U9-Forward's answer, one using filter and mean:

from statistics import mean

list1 = [50, 83, 26, 65, 92, 29, 77, 64]
average = mean(filter((50).__le__, list1))
print('%.2f' % average)


To answer the question of:


Please helps me to figure out the problems in my code


The issue is the lines

for count in marks
if count >= 50:
average = sum( count ) / len( count )


marks is a list of integers. Hence, when you loop for count in marks, the value of count is an integer. I tested your code in both Python 3.6.3 and 2.7.10, and you can't even call the sum() and len() functions on an integer (they both return a TypeError if you try).

You initialize average = [], so it seems like you expect average to contain a list, but even if sum( count ) = count and len( count ) = 1, then average contains an integer, not a list.

I'd be to curious to know which version of Python you're using that allows this code to execute without error.

Corrections for these errors have already been given.

Try this:

l=[i for i in list1 if i>=50]
print(sum(l)/len(l))


Or:

from statistics import mean
l=[i for i in list1 if i>=50]
print(mean(l))


If want to condition for empty lists:

l=[i for i in list1 if i>=50]
if l:
print(sum(l)/len(l))


Or:

from statistics import mean
l=[i for i in list1 if i>=50]
if l:
print(mean(l))


For python 2:

print(sum(l)/len(l))


Should be:

print(float(sum(l))/float(len(l)))


And no statistics module
Your code doesn't work because you're summing the iterator (an integer) not the list so that's why it's not working

Hope you are looking for this:

def get_pass_average(marks):
marksAbove = []
for count in marks:
if count >= 50:
marksAbove.append(count);

average = sum(marksAbove) / len(marksAbove)
return round(average,2)

def test_get_pass_average():
list1 = [50, 83, 26, 65, 92, 29, 77, 64]
print('%.2f' % (get_pass_average(list1)))

# Init
test_get_pass_average()


The following function gives you a general solution to what you need, the average of all numbers greater than or equal to a certain threshold, and allowing a specific result if no numbers are available (defaults to None):

def AverageWithThreshold(myList, threshold, emptyResult = None):
newList = [item for item in myList if item >= threshold]
if len(newList) == 0: return emptyResult
return sum(newList) / len(newList)


For your specific case, you can call it with something like (we assume the average of an empty list should be zero here):

print('%.2f' % (AverageWithThreshold(list1, 50, 0)))


Almost everything else is covered, filter has a use here as well

l = list(filter(lambda x: x > 50, marks))
print('%.2f' % (sum(l)/len(l)))



76.20