Saving text file in a for loop

Question

I'm trying to loop through a file, strip the sentences into individual lines, and then export that data.

filename = '00000BF8_ar.txt'

with open(filename, mode="r") as outfile:   
    str_output = outfile.readlines()
    str_output = ''.join(str_output)
    sentenceSplit = filter(None, str_output.split("."))

    for s in sentenceSplit:
        print(s.strip() + ".")
        #output += s 



        myfile = open(filename, 'w')
        myfile.writelines(s)
        myfile.close()

Unfortunately, it looks like the loop only goes through a few lines and saves them. So the whole file isn't looped through and saved. Any help on how I can fix that?

Answer 1

Here is the code I hope this is what you want to achieve,

filename = '00000BF8_ar.txt'

with open(filename, mode="r") as outfile:   
    str_output = outfile.readlines()
    str_output = ''.join(str_output)
    sentenceSplit = filter(None, str_output.split("."))
    l=[]

    for s in sentenceSplit:
        l.append(s.strip() + ".")
    myfile = open(filename, 'w')
    myfile.write('\n'.join(l))
    myfile.close()

Answer 2

Each time you re-open the file with the 'w' option, you basically erase its content.

Try modifying your code like this:

filename = '00000BF8_ar.txt'

with open(filename, "r") as infile:
    str_output = infile.readlines()

str_output = ''.join(str_output)
sentenceSplit = filter(None, str_output.split("."))

with open(filename, "w") as outfile:
    for s in sentenceSplit:
        print(s.strip() + ".")
        #output += s 
        s.writelines(s)

Another way to achieve the same thing would have been to open a new file using open(filename_new, 'a') which open a file for appending, but as a rule of thumb try not to open/close files inside a loop.

Answer 3

open(filename, 'w') will overwrite the file every time it starts. My guess is that what's currently happening is that only the last element in sentenceSplit is showing up in myfile .

The simple "solution" is to use append instead of write :

open(filename, 'a')

which will simply start writing at the end of the file, without deleting the rest of it.

However, as @chepner's comment states, why are you reopening the file at all? I would recommend changing your code to this:

with open(filename, mode="r") as outfile:   
    str_output = outfile.readlines()
    str_output = ''.join(str_output)
    sentenceSplit = filter(None, str_output.split("."))

with open(filename, mode='w') as myfile:
    for s in sentenceSplit:
        print(s.strip() + ".")
        myfile.writelines(s)

This way, instead of opening it many times, and overwriting it every time, you're only opening it once and just writing to it continuously.