Python读取大文件并拆分后：

Question

Based on this example of a line from a file

1:alpha:beta

I'm trying to get python to read the file in and then line by line print whats after the 2nd ':'

import fileinput
#input file

x = fileinput.input('ids.txt')
strip_char = ":"

for line in x:
    strip_char.join(line.split(strip_char)[2:])

This produces no results, however from a console session on a single line it works fine

Python 2.7.3rc2 (default, Apr 22 2012, 22:35:38) 
[GCC 4.6.3] on linux2
Type "help", "copyright", "credits" or "license" for more information.
data = '1:alpha:beta'
strip_char = ":"
strip_char.join(data.split(strip_char)[2:])
'beta'

What am i doing wrong please? Thanks

Answer 1

Values returned by functions aren't automatically sent to stdout in non-interactive mode, you have to explicitly print them.

So, for Python 2, use print line.split(strip_char, 2)[2] . If you ever use Python 3, it'll be print(line.split(strip_char, 2)[2]) .

(Props to Jon Clements, I forgot you could limit how many times a string will be split.)

Answer 2

For the data format given this will work:

 with open('data.txt') as inf:
    for line in inf:
        line = line.strip()
        line = line.split(':')
        print ':'.join(line[2:])

For '1:alpha:beta' the output would be 'beta'

For '1:alpha:beta:gamma' the output would be 'beta:gamma' (Thanks for @JAB pointing this out)

Answer 3

If it's everything after the 2nd ':' as a string (which can include ':') then use the maxsplit option, eg:

line.split(':', 2)[2]

eg:

>>> d = '1:alpha:beta:charlie:delta'
>>> d.split(':', 2)
['1', 'alpha', 'beta:charlie:delta']

This saves joining afterwards

Answer 4

You get just 'beta' because join gives you a string:

data = '1:alpha:beta'
strip_char = ":"
strip_char.join(data.split(strip_char)[2:])
'beta'

Try this:

lines=[]
with open('filePath', 'r') as f:
    for line in f.readlines():
        lines.append(line.strip())

for line in lines: print line.split(':')[1:]