concatinating 4 lines into a single line for a text file in python

Question

I have a text file which has the following data,

This is the pattern i have in my input file

i want the output file to have the following:

1111222233334444
5555666677778888
9999

That is, i am trying to merge the 4 line into a single line and write it to my output file.

I have written the below code, but somwhow it is not doing the job.Can anybody help me?

def open_file(filename):
    try:
        mod_list= []
        values = []
        for line in file(filename):

            line = line.rstrip()
            mod_list.append(line)

        i = iter(values)        
        for t in zip(*repeat(i, 4)):
            print(''.join(t))
            new_file.write(''.join(t)) 

        new_file.close() 
        file(filename).close()

    except Exception,e:
        print str(e)
        exit(1)

Are 1111, 2222, etc on separate lines in the input file, or is everything one line separated by spaces? How about the output? — pallgeuer, Apr 21 '20 at 10:03
What were the results of your debugging attempts? At what point exactly does the code do something you do not understand? — mkrieger1, Apr 21 '20 at 10:05
for t in zip(*repeat(i, 4)) seem to not combine the 4 lines into 1 for me — k11, Apr 21 '20 at 10:07
Then break it up in smaller parts. Apparently you do not understand how `zip`, `repeat` and `*args` work together. Maybe you could ask a more specific question about one of them. — mkrieger1, Apr 21 '20 at 10:09
I find this simple approach keeping your input string in the file "txt.txt" Try this: f= open('txt.txt','r') i=1 concat="" concat1="" mylist = []; for line in f: concat=concat+line.rstrip() if(i%4 == 0): mylist.append(concat) concat = "" concat1 = "" else: concat1 = concat1+line.rstrip() i=i+1 print(mylist[0:]) print("Remaining lines:",concat1) a second print will just print the remaining lines. It works!! — LOKENDRA, Apr 21 '20 at 11:31

Zabir Al Nazi · Answer 1 · 2020-04-21T10:14:23.890

-1

If they are multiple lines,

file.txt

Just take 4 chunks at a time and add it to a final list, finally write those strings with writelines().

a = open('file.txt', 'r').readlines()

final = []
buf = []
for line in a:
   if len(line.strip()) != 0:
       buf.append(line.strip())
   if len(buf) == 4:
       final.append(''.join(a for a in buf) + '\n')
       buf.clear()

outF = open("myOutFile.txt", "w")
outF.writelines(final)
outF.close()

edited Apr 21 '20 at 10:14

answered Apr 21 '20 at 10:08

Zabir Al Nazi

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better use %4 instead of ==4 in the if condition , to match it to n number of lines.. see this:I find this simple approach keeping your input string in the file "txt.txt" Try this: f= open('txt.txt','r') i=1 concat="" concat1="" mylist = []; for line in f: concat=concat+line.rstrip() if(i%4 == 0): mylist.append(concat) concat = "" concat1 = "" else: concat1 = concat1+line.rstrip() i=i+1 print(mylist[0:]) print("Remaining lines:",concat1) – LOKENDRA Apr 21 '20 at 11:32
2

What do you mean?? I cleared the array. Why do I need to check %4? – Zabir Al Nazi Apr 21 '20 at 11:34
aggreed !! I missed that "len" !! – LOKENDRA Apr 21 '20 at 11:39

score -1 · Answer 2 · edited Apr 22 '20 at 03:27

-1

Now lets optimize this for larger files:

with open(input_file) as f, open(output_file,'w') as res:
    while True:
        out = ''
        for j in range(4):
            out+=f.readline().strip()
        if out == '':
            break
        out+='\n'
        res.write(out)

Let:

l = open(filename,'r').splitlines()
>>>l
[1111, 2222, 3333 ,4444, 5555, 6666, 7777, 8888 ,9999]

Now we will create the pairs:

l = [l[i:i+4] for i in range(0,len(l),4)]
>>> l
[[1111, 2222, 3333, 4444], [5555, 6666, 7777, 8888], [9999]]
Now we will create the line for the output text:
out = '\n'.join(''.join(str(j) for j in i) for i in l)
>>> out
1111222233334444
5555666677778888
9999

Now write out to the output file:

f = open(output_file,'w')
f.write(out)
f.close()

edited Apr 22 '20 at 03:27

tripleee

175,061
34
275
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answered Apr 21 '20 at 10:11

Joshua Varghese

5,082
1
13
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1

Not my downvote, but reading the entire input into memory is not scalable to large files. – tripleee Apr 21 '20 at 10:13
@tripleee so you mean the input file must be edited? – Joshua Varghese Apr 21 '20 at 10:15
1

No, I mean you only need to have a maximum of four lines in memory at any one time. – tripleee Apr 21 '20 at 10:15
Not particularly, no. Just read four lines at a time until there are no more lines to read. You don't need to know ahead of time how many lines there will be. – tripleee Apr 21 '20 at 11:04
@tripleee well now? – Joshua Varghese Apr 21 '20 at 11:13
downvoters, care to comment? – Joshua Varghese Apr 21 '20 at 11:23
Yeah, better, though you should probably use a context manager (`with open(...):`) – tripleee Apr 21 '20 at 11:25

score -1 · Accepted Answer · answered Apr 21 '20 at 10:31

Check this solution. Make sure to remove the new line character before writing the content into the output file and write a new line when needed.

max_line = 4
count=0

with open('output_file_name', 'a') as out_file, open('input_file_name','r') as in_file:
    for line in in_file:
        out_file.write(line.strip('\n'))
        count += 1
        if count == 4:
            out_file.write('\n')
            count=0
    out_file.write('\n')

concatinating 4 lines into a single line for a text file in python

3 Answers3