Average -Python

Question

I am trying to find the average of numbers in ranges (i.e. find the average of all numbers in range 1-1000). I wrote the following code to do this, but the due to the if-statement, when run, the code produces multiple numbers. I then tried a while-loop instead, but when I entered a break statement, it produced the same list the if-statement produced. Is there any way to use an if-statement and get 1 single number that is the average? Thank you!

mylist =[]
def ave_data(x, y):
    for line in filename:    
        for number in line.split():
            if int(number) > x and int(number) < y:
                mylist.append(int(number)) 
                print(sum(mylist)/len(mylist))

your `print` statement is in the loop so will be done every time through. Just move it outside of the for-loop so it's done once after `mylist` is populated. — Always Learning, Jul 19 '17 at 14:48
Possible duplicate: https://stackoverflow.com/questions/9039961/finding-the-average-of-a-list — EsotericVoid, Jul 19 '17 at 14:49

Willem Van Onsem · Answer 1 · 2017-07-19T14:50:28.640

It is not due to the if statement. You simply put the print(..) in the if in the for loop. By moving it outside the outer for, it will print the average for the entire file:

def ave_data(x, y):
    mylist = []  # move inside
    for line in filename:    
        for number in line.split():
            if int(number) > x and int(number) < y:
                mylist.append(int(number)) 
    print(sum(mylist)/len(mylist))  # for the entire file.

You also move the mylist variable better inside the function. Otherwise it is a global variable, and other functions can alter it. Furthermore a second run would take the average of the two files.

That being said, you make things too complicated. You can simply use:

def ave_data(x, y):
    mylist = [int(number) for line in filename for number in line.split()
                          if x < int(number) < y]
    print(sum(mylist)/len(mylist))  # for the entire file.

Wow I can't believe I missed that. Thank you! – H. Minear Jul 19 '17 at 14:50 — H. Minear, Jul 19 '17 at 14:50

Mohd · Answer 2 · 2017-07-19T14:52:46.747

2

You can also use list-comprenehsion instead of for-loop, as the following:

mylist = [int(num) for line in filename for num in line.split() if y > int(num) > x]
print sum(mylist) / len(mylist)

You can also add a condition to check if the list is empty:

print sum(mylist) / len(mylist) if mylist else 'No numbers in that range'

edited Jul 19 '17 at 14:52

answered Jul 19 '17 at 14:51

Mohd

5,523
7
19
30

Thank you for your help! – H. Minear Jul 19 '17 at 14:52
Glad to help :-) – Mohd Jul 19 '17 at 14:58

score 0 · Answer 3 · answered Jul 19 '17 at 14:53

You are seeing multiple numbers because your print statement is within your for loop. Take a look at this pseudocode:

create an empty list
open the file
for each line in the file
    for each number in the line
        if the number is within the range
            add the number to the list
            compute the average of the list of numbers

You see, you are computing the average every time you find a number within the required range. Instead, what you want to do is to gather all the numbers first (within the for loop), and then (outside the for loop) compute the average:

create an empty list
open the file
for each line in the file
    for each number in the line
        if the number is within the range
            add the number to the list
compute the average of the list of numbers

This is achieved with this code:

def ave_data(x, y):
    nums = []
    for line in filename:    
        for number in line.split():
            if int(number) > x and int(number) < y:
                nums.append(int(number)) 
    print(sum(mylist)/len(mylist))

Here's a slightly better way to do the same thing:

def ave_data(x,y):
    total = 0
    nums = 0
    with open('path/to/file') as infile:
        for line in infile:
            for num in line.split():
                num = int(num)
                if not (x < num < y): continue
                total += num
                nums += 1

    if not nums:
        print("There were no numbers within the required range")
        return

    print("The average is", total/nums)

Average -Python

3 Answers3

Linked