Python: How to Calculate the Sum of Numbers from a File

How to calculate the sum of numbers in one file and print the result into another file in Python?

The lines you're reading from the input file are strings so you need to convert them to ints. Also, each line will have a newline character '\n' at the end which will need to be removed before you can successfully convert each line to an int.

There are also several other issues with your code example. Sum is a list, but aren't you trying to add each int from input.txt? Also if i.isdigit() is not indented. try, except can be used instead though.

x = open("input.txt", "r")
Sum = 0
z = x.readlines()
for i in z:
    try:
        Sum += int(i.strip())
    except ValueError:
        pass

x.close()
y= open ("output.txt", "w")
y.write(str(Sum))
y.close()

Python: How do I calculate the sum of numbers from a file?

Keep it simple:

with open('data.txt', 'r') as f:
    result = sum(map(int, f))

int is mapped over each line from f, then sum() adds up the resulting integers.

How to sum numbers from a text file in Python

I have a code that relies on me reading a text file, printing off the
numbers where there are numbers, printing off specific error messages
where there are strings instead of numbers, then summing ALL the
numbers up and printing their sum (then saving ONLY the numbers to a
new text file).

So you have to do the following:

1. Print numbers
2. Print a message when there isn't a number
3. Sum the numbers and print the sum
4. Save only the numbers to a new file

Here is one approach:

total = 0

with open('input.txt', 'r') as inp, open('output.txt', 'w') as outp:
   for line in inp:
       try:
           num = float(line)
           total += num
           outp.write(line)
       except ValueError:
           print('{} is not a number!'.format(line))

print('Total of all numbers: {}'.format(total))

Python : Sum of numbers in different files

Assuming you know the file format beforehand and have a list of file names, you just iterate over the files and accumulate the sums in a list of lists of the right size:

nrows, ncols = 2, 5          # 800, 800 in your real code
sums = [[0] * ncols for _ in range(nrows)]

file_names = ["file1.txt", "file2.txt"]
for file_name in file_names:
    with open(file_name) as f:
        for i, row in enumerate(f):
            for j, col in enumerate(row.split()):
                sums[i][j] += int(col)

for row in sums:
    print(*row)
# 29 88 81 55 43
# 65 64 34 70 99

---

Alternatively using numpy.loadtxt:

import numpy as np

sum(np.loadtxt(file_name, dtype=int) for file_name in file_names)
# array([[ 29,  88,  81,  55,  43],
#        [ 65,  64,  34,  70,  99]])

How can I sum integers from multiple text files into a new text file using python?

I'd use generators so you don't have to load all of the files into memory at once (in case they're large)

Then just pull the next value from each generator, sum them, write them and carry on. When you hit the end of the file you'll get a StopIteration exception and be done

def read_file(file):
  with open(file, "r") as inFile:
    for row in inFile:
      yield row

file_list = ["file1.txt", "file2.txt", ..., "file10.txt"]
file_generators = [read_file(path) for path in file_list]

with open("totals.txt", "w+") as outFile:
  while True
    try:
      outFile.write(f"{sum([int(next(gen)) for gen in file_generators])}\n")
    except StopIteration:
      break

How do I print the sum of the numbers into the output file

Try the following.

I just added a line outp.write('\n'+str(total)) to add the sum of numbers after the for loop finishes calculating the sum

total = 0

with open('numbers.txt', 'r') as inp, open('outputnumbers.txt', 'w') as outp:
   for line in inp:
       try:
           num = float(line)
           total += num
           outp.write(line)
       except ValueError:
           print('{} is not a number!'.format(line))
   outp.write('\n'+str(total))

print('Total of all numbers: {}'.format(total))

numbers.txt

1
2
3
4
5
6
7
8
9
10

outputnumbers.txt

1
2
3
4
5
6
7
8
9
10
55.0

---

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