How do I split a multi-line string into multiple lines?

I have a multi-line string that I want to do an operation on each line, like so:

inputString = """Line 1
Line 2
Line 3"""

I want to iterate on each line:

for line in inputString:
    doStuff()

Answers:

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Method 1

inputString.splitlines()

Will give you a list with each item, the splitlines() method is designed to split each line into a list element.

Method 2

Like the others said:

inputString.split('n')  # --> ['Line 1', 'Line 2', 'Line 3']

This is identical to the above, but the string module’s functions are deprecated and should be avoided:

import string
string.split(inputString, 'n')  # --> ['Line 1', 'Line 2', 'Line 3']

Alternatively, if you want each line to include the break sequence (CR,LF,CRLF), use the splitlines method with a True argument:

inputString.splitlines(True)  # --> ['Line 1n', 'Line 2n', 'Line 3']

Method 3

Use inputString.splitlines().

Why splitlines is better

splitlines handles newlines properly, unlike split.

It also can optionally return the newline character in the split result when called with a True argument, which is useful in some specific scenarios.

Why you should NOT use split("n")

Using split creates very confusing bugs when sharing files across operating systems.

n in Python represents a Unix line-break (ASCII decimal code 10), independently of the OS where you run it. However, the ASCII linebreak representation is OS-dependent.

On Windows, n is two characters, CR and LF (ASCII decimal codes 13 and 10, r and n), while on modern Unix (Mac OS X, Linux, Android), it’s the single character LF.

print works correctly even if you have a string with line endings that don’t match your platform:

>>> print " a n b rn c "
 a 
 b 
 c

However, explicitly splitting on “n”, has OS-dependent behaviour:

>>> " a n b rn c ".split("n")
[' a ', ' b r', ' c ']

Even if you use os.linesep, it will only split according to the newline separator on your platform, and will fail if you’re processing text created in other platforms, or with a bare n:

>>> " a n b rn c ".split(os.linesep)
[' a n b ', ' c ']

splitlines solves all these problems:

>>> " a n b rn c ".splitlines()
[' a ', ' b ', ' c ']

Reading files in text mode partially mitigates the newline representation problem, as it converts Python’s n into the platform’s newline representation.

However, text mode only exists on Windows. On Unix systems, all files are opened in binary mode, so using split('n') in a UNIX system with a Windows file will lead to undesired behavior. This can also happen when transferring files in the network.

Method 4

Might be overkill in this particular case but another option involves using StringIO to create a file-like object

for line in StringIO.StringIO(inputString):
    doStuff()

Method 5

The original post requested for code which prints some rows (if they are true for some condition) plus the following row.
My implementation would be this:

text = """1 sfasdf
asdfasdf
2 sfasdf
asdfgadfg
1 asfasdf
sdfasdgf
"""

text = text.splitlines()
rows_to_print = {}

for line in range(len(text)):
    if text[line][0] == '1':
        rows_to_print = rows_to_print | {line, line + 1}

rows_to_print = sorted(list(rows_to_print))

for i in rows_to_print:
    print(text[i])

Method 6

I wish comments had proper code text formatting, because I think @1_CR ‘s answer needs more bumps, and I would like to augment his answer. Anyway, He led me to the following technique; it will use cStringIO if available (BUT NOTE: cStringIO and StringIO are not the same, because you cannot subclass cStringIO… it is a built-in… but for basic operations the syntax will be identical, so you can do this):

try:
    import cStringIO
    StringIO = cStringIO
except ImportError:
    import StringIO

for line in StringIO.StringIO(variable_with_multiline_string):
    pass
print line.strip()

All methods was sourced from stackoverflow.com or stackexchange.com, is licensed under cc by-sa 2.5, cc by-sa 3.0 and cc by-sa 4.0