Calculating Arithmetic Mean (One Type of Average) in Python

Calculating arithmetic mean (one type of average) in Python

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().

Simple arithmetic average in Python

n = input('Number of terms')
acc = 0
for i in range(1,int(n)+1):
    a=input('Term number '+str(int(i))+': ')
    acc += float(a)
print('The average is ',acc/int(n))

The idea is to create an accumulator variable acc to which the entered numbers are added. After the loop acc is equal to the sum of all numbers entered. Divide it by the number of terms and you get the arithmetic average.

Finding the average of a list

For Python 3.8+, use statistics.fmean for numerical stability with floats. (Fast.)

For Python 3.4+, use statistics.mean for numerical stability with floats. (Slower.)

xs = [15, 18, 2, 36, 12, 78, 5, 6, 9]

import statistics
statistics.mean(xs)  # = 20.11111111111111

For older versions of Python 3, use

sum(xs) / len(xs)

For Python 2, convert len to a float to get float division:

sum(xs) / float(len(xs))

Arithmetic mean for 'i' elements

The simplest and most efficient way is to keep separately the sum and the count of element of the input list. Then the arithmetic mean if just the current sum divided by the current count:

def mari(x):
    s = 0.0 # current sum
    cnt = 0 # current count
    m = [] # list to return
    for i in x:
        s += i
        cnt += 1
        m.append(s / cnt)
    return m

Calculating arithmetic mean from a list

Your code is quite verbose but correct nonetheless. Below, you can find a more pythonic solution:

import random

numberList = []
for _ in range(1000):
    numberList.append(random.randrange(1, 7))

# or simply using a list comprehension
# numberList = [random.randrange(1, 7) for _ in range(1000)]

print(sum(numberList)/len(numberList))  # I got 3.587, 3.556, 3.529 which is close to what you would expect (3.5)

Note that the solution proposed above saves memory as well as it does not define as many variables (x, count, list_sum)

How to calculate mean in python?

Convert you list from strings to np.float:

>>> gp = np.array(goodPix, np.float)
>>> np.mean(gp)
96.906260000000003

Calculating the average of specific numbers in a mixed text file?

You need to represent the data, currently you are returning tuples from reading the file.
Store them in a list, create methods to filter your students on theire major and one that creates the avgGPA of a given student-list.

You might want to make the GPA a float on reading:

with open("s.txt","w") as f:
    f.write("OLIVER\n8117411\nEnglish\n2.09\nOLIVIA\n6478288\nLaw\n3.11\n" + \
            "HARRY\n5520946\nEnglish\n1.88\nAMELIA\n2440501\nFrench\n2.93\n")

def readStudents6(file):
    name = file.readline().rstrip()
    studentID = file.readline().rstrip()
    major = file.readline().rstrip()
    gpa = float(file.readline().rstrip())  # make float
    return name, studentID, major, gpa

Two new helper methods that work on the returned student-data-tuples:

def filterOnMajor(major,studs):
    """Filters the given list of students (studs) by its 3rd tuple-value. Students
    data is given as (name,ID,major,gpa) tuples inside the list."""
    return [s for s in studs if s[2] == major] # filter on certain major

def avgGpa(studs):
    """Returns the average GPA of all provided students. Students data
    is given as (name,ID,major,gpa) tuples inside the list."""
    return sum( s[3] for s in studs ) / len(studs) # calculate avgGpa

Main prog:

students = []

with open("s.txt","r") as f:
    while True:
        try: 
            stud = readStudents6(f)
            if stud[0] == "":
                break
            students.append( stud )
        except:
            break

print(students , "\n")

engl = filterOnMajor("English",students)

print(engl, "Agv: ", avgGpa(engl))

Output:

# all students    (reformatted)
[('OLIVER', '8117411', 'English', 2.09), 
 ('OLIVIA', '6478288', 'Law', 3.11), 
 ('HARRY', '5520946', 'English', 1.88), 
 ('AMELIA', '2440501', 'French', 2.93)] 

# english major with avgGPA    (reformatted)
[('OLIVER', '8117411', 'English', 2.09), 
 ('HARRY', '5520946', 'English', 1.88)] Agv:  1.9849999999999999

See: PyTut: List comprehensions and Built in functions (float, sum)

---

def prettyPrint(studs):
    for name,id,major,gpa in studs:
        print(f"Student {name} [{id}] with major {major} reached {gpa}")

prettyPrint(engl)

Output:

Student OLIVER [8117411] with major English reached 2.09
Student HARRY [5520946] with major English reached 1.88

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