Read text file to list in python

Question

I want to create a text file which contains positive/negative numbers separated by ','. i want to read this file and put it in data = []. i have written the code below and i think that it works well. I want to ask if you guys know a better way to do it or if is it well written thanks all

#!/usr/bin/python
if __name__ == "__main__":
        #create new file
        fo = open("foo.txt", "w")
        fo.write( "111,-222,-333");
        fo.close()
        #read the file
        fo = open("foo.txt", "r")
        tmp= []
        data = []
        count = 0
        tmp = fo.read() #read all the file

        for i in range(len(tmp)): #len is 11 in this case
            if (tmp[i] != ','):
                count+=1
            else:
                data.append(tmp[i-count : i]) 
                count = 0

        data.append(tmp[i+1-count : i+1])#append the last -333
        print data
        fo.close()

Please see Code Review for feedback on working code.

user2201041
– user2201041

2017-03-06 13:49:57 +00:00
Commented Mar 6, 2017 at 13:49 — user2201041
– user2201041, Commented Mar 6, 2017 at 13:49

anairebis · Accepted Answer · 2017-03-06 13:52:56Z

1

You can use split method with a comma as a separator:

fin = open('foo.txt')
for line in fin:
    data.extend(line.split(','))
fin.close()

answered Mar 6, 2017 at 13:52

anairebis

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2 Comments

gab55 Over a year ago

thanks for your help, i need to append the numbers as float for further code..i tried data.extend(float(line.split(',')) but it seems not to work. i need like this data.append(float(tmp[i-count : i]))

anairebis Over a year ago

line.split(',') returns a list, and you can't apply float to the list directly. If you want to apply it to each element of that list you can use map method: data.extend(map(float, line.split(','))) or for you to better understand it, map(float, line.split(',')) means [float(num) for num in line.split(',')]

Kewl · Accepted Answer · 2017-03-06 13:59:54Z

0

Instead of looping through, you can just use split:

#!/usr/bin/python
if __name__ == "__main__":
        #create new file
        fo = open("foo.txt", "w")
        fo.write( "111,-222,-333");
        fo.close()
        #read the file
        with open('foo.txt', 'r') as file:
            data = [line.split(',') for line in file.readlines()]
        print(data)

Note that this gives back a list of lists, with each list being from a separate line. In your example you only have one line. If your files will always only have a single line, you can just take the first element, data[0]

edited Mar 6, 2017 at 13:59

answered Mar 6, 2017 at 13:51

Kewl

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Comments

Anand Tripathi · Accepted Answer · 2017-03-06 14:00:02Z

0

To get the whole file content(numbers positive and negative) into list you can use split and splitlines

file_obj = fo.read()#read your content into string
list_numbers = file_obj.replace('\n',',').split(',')#split on ',' and newline
print list_numbers

answered Mar 6, 2017 at 14:00

Anand Tripathi

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