Adding numbers within a text file (python)

Question

Hi i have been given a task to read these numbers from within a text file "1,3,5,7,9,11,13,15," and to add them together how would i do this? So far i have:

file = open("C:\\Users\\Dylan\\Python\\OddNumbersAns.txt", "r")
line = file.read()
intline = int(line)
print(intline)

But i recieve this error:

Traceback (most recent call last):
  File "C:\Users\Dylan\Python\text file add.py", line 3, in <module>
    intline = int(line)
ValueError: invalid literal for int() with base 10: '1, 3, 5, 7, 9, 11, 13, 15, '

Thanks

Answer:

file = open("C:\\Users\\Dylan\\Python\\OddNumbersAns.txt", "r")

line = file.read()

line.split(",")

print (line.split(","))

total = sum([int(num) for num in line.split(',')])

print(total)

You're trying to turn the entire line into a single integer. You need to split it up into separate strings first, going by the commas. Investigate the split function. — Mark Reed
– Mark Reed, Commented Jan 26, 2014 at 16:40

Stephan · Accepted Answer · 2014-01-26 17:03:28Z

2

You want the sum() function, after splitting the line on every comma:

total = sum(int(num) for num in line.split(','))

Don't try to call int(line), as that's trying to turn the whole line into a single int.

Instead, you split the line on every comma, yielding a sequence of strings, each of which is cast to int. Putting the whole thing in the sum function adds them together.

edited Jan 26, 2014 at 17:03

answered Jan 26, 2014 at 16:46

Stephan

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3 Comments

Paulo Bu Over a year ago

Don't need to make the list, you can call sum like this: total = sum(int(num) for num in line.split(',')). Probably will increases a little in performance. +1 for using sum.

utdemir Over a year ago

total = sum(map(int, line.split(',')). Even if BDFL doesn't like it, it looks more concise and clear to me.

Stephan Over a year ago

@PauloBu - you're right, of course. The inclusion of the list was redundant here; I've removed it.

zhangxaochen · Accepted Answer · 2014-01-26 17:02:02Z

0

If your file contains trailing new line or comma:

#a.txt
1, 3, 5, 7, 9, 11, 13, 15, 
2, 3, 45, 6,

you need to strip it first, then split:

In [174]: with open('a.x', 'r') as f:
     ...:     line=f.read()
     ...:     total=sum(map(int, line.strip(', \n').split(',')))
     ...:     print total
#output: 120

without strip, e.g. '1,2,\n' would be splitted into ['1', '2', '\n'], and int('\n') or int('') would raise a ValueError.

edited Jan 26, 2014 at 17:02

answered Jan 26, 2014 at 16:56

zhangxaochen

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Comments

Siva Cn · Accepted Answer · 2014-01-26 17:03:40Z

0

This is the basic stuff you need

>>> txt_line = "1, 2, 3, 4, 5, 6, 7, 8"
>>> 
>>> [int(ele.strip()) for ele in txt_line.split(",")]
[1, 2, 3, 4, 5, 6, 7, 8]
>>> sum([int(ele.strip()) for ele in txt_line.split(",")])
36
>>>

In addition to this you may have to take care of the file inputs It could either be complete file content or line by line read So I would recommend the following

with open('input_file.txt', 'r') as fp:
    line = fp.readline()
    while line:
        ## Here insert the above logic
        line = fp.readline()

answered Jan 26, 2014 at 17:03

Siva Cn

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