在Python中将文本文件的每个值移至其各自的行

Question

This is a fairly simple question but I would like to know how to put each section of this text file into it's own line, for example like this:

0.00000159
volume
645453536.89920200
lasttradetime

Thanks!

Answer 1

lines = open("textfile").read().split()

That will split the whole file in parts using blanks (spaces, tabs, etc) as the separator. If you want to save it again to a file, each one on a line:

open("newtextfile", "w").write('\n'.join(lines))

Answer 2

Looking at your file makes me think that you want the last trade times to be kept together, eg

0.00000159
volume
645453536.89920200
lasttradetime
2014 03 06 10 32 03

So I'd recommend something like

import re
with open("infile.txt") as fp_in, open("outfile.txt", "w") as fp_out:
    d = fp_in.read()
    parts = re.split(r"\s\s+", d)
    for part in parts:
        fp_out.write(part + "\n")

which will achieve that. (Probably be marginally faster to combine the parts and do one write, like "\\n".join(parts) + "\\n" .)

Answer 3

To support arbitrary large files that might not fit in memory, you could use mmap :

#!/usr/bin/env python
import re
from mmap import ACCESS_READ, mmap

with open('filename', 'rb') as file:
    mm = mmap(file.fileno(), 0, access=ACCESS_READ)
    try:
        with open('output', 'wb') as output_file:
            for m in re.finditer(r'\S+', mm):
                print >>output_file, m.group()
    finally:
        mm.close()