Regular Expression for Finding Numbers in a Line (Python)

Question

I'm just learning about regular expressions and I need to read in a text file and find every instance of a number and find the sum of all the numbers.

import re

sum = 0
list_of_numbers = list()
working_file = open("sample.txt", 'r')
for line in working_file:
    line = line.rstrip()
    working_list = re.findall('[0-9]+', line)
    if len(working_list) != 1:
        continue
    print(working_list)
    for number in working_list:
        num = int(number)
        list_of_numbers.append(num)
for number in list_of_numbers:
    sum += number
print(sum)

I put the print(working_list) in order to try and debug it and see if all the numbers are getting found correctly and I've seen, by manually scanning the text file, that some numbers are being skipped while others are not. I'm confused as to why as I thought my regular expression guaranteed that any string with any amount of digits will be added to the list.

Here is the file.

if len(working_list) != 1 ... im pretty sure thats not what you want... note you *really dont even have to check if the working_list has numbers at all... — juanpa.arrivillaga
– juanpa.arrivillaga, Commented Jan 3, 2018 at 22:36
so, you just need to do total = sum(int(x) for line in working_file for x in re.findall('[0-9]+', line)) — juanpa.arrivillaga
– juanpa.arrivillaga, Commented Jan 3, 2018 at 22:38

Engineero · Accepted Answer · 2018-01-03 22:46:15Z

6

You're only validating lines that have ONLY one number, so a line with two numbers will be skipped because of if len(working_list) != 1: continue, that basically says "if there isn't EXACTLY one number on this line then skip", you may have meant something like if len(working_list) < 1: continue

edited Jan 3, 2018 at 22:46

Engineero

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answered Jan 3, 2018 at 22:36

Dash Winterson

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1 Comment

Jesse R Over a year ago

Oh wow! Silly error on my part I don't know how I didn't see that! Thank you!!

Dash Winterson · Accepted Answer · 2019-10-14 21:49:08Z

0

I would do it like:

import re

digits_re = re.compile(r'(\d+(\.\d+)?)') 
with open("sample.txt", 'r') as fh:
  numbers = [float(match[0]) for match in digits_re.findall(fh.read())]
print(sum(numbers))

or like you're doing with ints just

import re

digits_re = re.compile(r'(\d+)') 
with open("sample.txt", 'r') as fh:
  numbers = [int(match[0]) for match in digits_re.findall(fh.read())]
print(sum(numbers))

answered Oct 14, 2019 at 21:49

Dash Winterson

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Comments

4b0 · Accepted Answer · 2021-05-18 12:24:42Z

0

h = open('file.txt')
nos = list()
for ln in h:
    fi = re.findall('[0-9]+', ln)
    for i in fi:
        nos.append(int(i))
print('Sum:', sum(nos))

edited May 18, 2021 at 12:24

4b0

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answered May 18, 2021 at 12:23

sasiadr

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1 Comment

4b0 Over a year ago

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