ValueError: could not convert string to float — user input with Python

Question

I'm trying to write a 'while' loop that takes a users input, if it is a number it remembers it, if it is a blank space it breaks. At the end it should print the average of all entered numbers. This is giving me the error 'could not convert string to float: '. What exactly is wrong here? Thanks!

EDIT: I re-wrote it like this and I get the same error about converting, but it seems to be on the final (count += 1) line?

number = 0.0
count = 0

while True:
    user_number = input('Enter a number: ')
    if user_number == ' ':
        break
        print (number / count)
    number = number + float(user_number)
    count += 1

The issue is in the order, even if you enter blank space, you still try to convert it to float in - number = number + float(user_number) . — Anand S Kumar
– Anand S Kumar, Commented Aug 18, 2017 at 5:03
Is the user entering characters other than ' ' and numbers? — nikpod
– nikpod, Commented Aug 18, 2017 at 5:11

cs95 · Accepted Answer · 2017-08-18 05:19:15Z

2

My guess is that you directly hit enter when you don't want to pass numbers anymore. In that case, comparing with a space is incorrect.

number = 0.0
count = 0

while True:
    user_number = input('Enter a number: ')
    if user_number == '':
        break

    number += float(user_number)
    count += 1

print (number / count)

Also a statement after a break is unreachable.

If you want a cleaner alternative, I would recommend appending to a list, and then computing the average. This removes the need for a separate counter. Try this:

numbers = []
while True:
    user_number = input('Enter a number: ')
    if user_number == '':
        break            

    numbers.append(float(user_number))

print (sum(numbers) / len(numbers))

Additionally, you could remove the need for a break by testing in the head of while, but you'll need to take an additional input outside the loop.

edited Aug 18, 2017 at 5:19

answered Aug 18, 2017 at 5:16

cs95

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1 Comment

G3ck0 Over a year ago

Ah, that's it! It wasn't a blank space, just nothing! Thank you so much.

Shaido · Accepted Answer · 2017-08-18 05:15:41Z

0

You should change the order, right now you try to convert everything into floats, even blank spaces.

while True:
    user_number = input('Enter a number: ')
    if not user_number.isdigit():
        print (number / count)
        break
    count += 1
    number = number + float(user_number)

Additionally, you should do the print of the average value before the break.

I changed your if condition to break if any input except a number is entered, it should be a bit more general than before.

edited Aug 18, 2017 at 5:15

answered Aug 18, 2017 at 5:08

Shaido

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2 Comments

Shaido Over a year ago

@G3ck0 I changed it to break when anything except a number is entered. It accounts for cases where other string than numbers and blank spaces are used.

G3ck0 Over a year ago

It's a program for uni, weekly exercises. Nothing will one entered other than numbers or a blank space.

Hafiz Muhammad Shafiq · Accepted Answer · 2017-08-18 05:19:08Z

0

Change order and it should solve the problem, you should first check is enterned input is string or not then go to number part

#!/usr/bin/python
number = 0.0
count = 0

while True:
    user_number = raw_input('Enter a number: ')
    if user_number == (' '):        
        print (number / count)
    break
    number = number + float(user_number)
    count += 1

edited Aug 18, 2017 at 5:19

answered Aug 18, 2017 at 5:09

Hafiz Muhammad Shafiq

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1 Comment

G3ck0 Over a year ago

Even that still gives me the 'could not convert string to float:' error...

dinesh kumar · Accepted Answer · 2017-08-18 05:28:37Z

0

This should work for you.

lst= []
while True:
user_number = input('Enter a number: ')
if user_number == ' ':
    break
lst.append(int(user_number))
print(int(user_number))
print("Average : " + str(sum(lst)/len(lst)))

answered Aug 18, 2017 at 5:28

dinesh kumar

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3 Comments

Gahan Over a year ago

and what you think my posting similar answer?

cs95 Over a year ago

It certainly does not work, because it suffers from severe formatting and indentation problems.

dinesh kumar Over a year ago

@cᴏʟᴅsᴘᴇᴇᴅ.. you are right , my code has indentation issues as it appears here..because i am new to this community and not exactly sure how to put my working code in the comments. I apologize, but my code certainly works perfect, i have tested it before posting the code..please apply appropriate indentation to my code..it will work

Rithesh B · Accepted Answer · 2017-08-18 07:17:41Z

0

This code works correctly. I think you are giving Other than space as input to break.

number = 0.0
count = 0

while True:
    user_number = input('Enter a number: ')
    if user_number == ' ':
        break
        print (number / count)
    number = number + float(user_number)
    count += 1

or else use below code: --> Break will be triggered for non-digit input.

number = 0.0
count = 0
while True:
    user_number = input('Enter a number: ')
    if not user_number.isdigit():
        break
    number = number + float(user_number)
    count += 1
print("user_number", number)
print("Count", count)
print (number / count)

edited Aug 18, 2017 at 7:17

answered Aug 18, 2017 at 6:05

Rithesh B

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