Python - Rounding floating integers defined as variables and displaying them

Question

I am trying to get this to calculate a number based on user input. While displaying it I want it to round to 2 digits. It refuses too! So confused. Any advice?

def calc(user_id):
numbers = {'A': 4, 'B': 3, 'C': 2, 'D': 1, 'F': 0}
user = User.objects.get(pk=user_id)
user_profile = UserProfile.objects.get(user=user)
outs = Out.objects.filter(user=user)
counter = 0
total_number = 0
for out in outs:
if out.data['type'] != 'panel':
continue
else:
print out.data
total_number += numbers[out.data['level']]
counter += 1
x = round(float(total_number/float(counter)), 2)
user_profile.average = x
user_profile.save()

What exactly is getting displayed? This could be a case of floating-point math inaccuracy. — TheSoundDefense
– TheSoundDefense, Commented Aug 9, 2014 at 2:16

Juan David · Accepted Answer · 2014-08-09 03:47:30Z

1

Check this line of code:

total_number += numbers[out.data['level']]

if you are receiving a Keyerror, your problem is in that particular line. If you post your code indented, is going to be much more readable

def calc(user_id):

    numbers = {'A': 4, 'B': 3, 'C': 2, 'D': 1, 'F': 0}
    user = User.objects.get(pk=user_id)
    user_profile = UserProfile.objects.get(user=user)
    outs = Out.objects.filter(user=user)
    counter = 0
    total_number = 0

    for out in outs:
        if out.data['type'] != 'panel':
            continue
        else:
            print out.data
        total_number += numbers[out.data['level']]
        counter += 1

    x = round(float(total_number/float(counter)), 2)
    user_profile.average = x
    user_profile.save()

UPDATE

If you need precision, work with fixed and floating point arithmetic. check this module

http://pymotw.com/2/decimal/

Also, its posible that your round command works correctly but your number cannot be represented exactly in binary floating point. If you need to print the number you can use:

"%.1f" % n

edited Aug 9, 2014 at 3:47

answered Aug 9, 2014 at 2:28

Juan David

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3 Comments

SudoFox Over a year ago

There is no error presented, it generates but it simply doesn't round the number. Thank you for the indents! I will make sure to do that next time.

Juan David Over a year ago

You are welcome, please edit your post with more details like examples of your output or little pieces of data input

Juan David Over a year ago

Also you dont need to cast to float twice in float(total_number/float(counter)). Just put round(total_number/float(counter), 2). Maybe that's causing your problem

Community · Accepted Answer · 2017-05-23 10:33:32Z

0

I don't believe you need to use round().

The string formatting is the way to go. See here: Formatted strings for rounding in python

edited May 23, 2017 at 10:33

CommunityBot

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answered Aug 9, 2014 at 12:35

joel goldstick

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