Why changing line in string in Python (\n) doesn't work?

Question

In most cases it does the job, but sometimes (it's hard for my to precise, what does it depend on) it falls into an infinite loop, as it doesn't slice the text string.

def insertNewlines(text, lineLength):
    """
    Given text and a desired line length, wrap the text as a typewriter would.
    Insert a newline character ("\n") after each word that reaches or exceeds
    the desired line length.

    text: a string containing the text to wrap.
    line_length: the number of characters to include on a line before wrapping
        the next word.
    returns: a string, with newline characters inserted appropriately. 
    """

    def spacja(text, lineLength):
        return text.find(' ', lineLength-1)

    if len(text) <= lineLength:
        return text
    else:
        x = spacja(text, lineLength)
        return text[:x] + '\n' + insertNewlines(text[x+1:], lineLength)

works with all cases I tried except for

 insertNewlines('Random text to wrap again.', 5)

and

insertNewlines('mubqhci sixfkt pmcwskvn ikvoawtl rxmtc ehsruk efha cigs itaujqe pfylcoqw iremcty cmlvqjz uzswa ezuw vcsodjk fsjbyz nkhzaoct', 38)

I have no idea why.

perhaps posting the code for insertNewlines would herlp ...

ennuikiller
– ennuikiller

2013-03-17 12:50:27 +00:00
Commented Mar 17, 2013 at 12:50 — ennuikiller
– ennuikiller, Commented Mar 17, 2013 at 12:50

Martijn Pieters · Accepted Answer · 2013-03-17 13:01:48Z

5

Don't re-invent the wheel, use the textwrap library instead:

import textwrap

wrapped = textwrap.fill(text, 38)

Your own code does not handle the case where no space has been found and spacja returns -1.

edited Mar 17, 2013 at 13:01

answered Mar 17, 2013 at 12:54

Martijn Pieters

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2 Comments

jfs Over a year ago

you might mean textwrap.fill().

Martijn Pieters Over a year ago

@J.F.Sebastian: Indeed, .wrap() returns a list, .fill() joins them with newlines.

uselpa · Accepted Answer · 2013-03-17 12:58:21Z

1

You are missing the case when find returns -1 (i.e. not found).

Try:

if len(text) <= lineLength:
    return text
else:
    x = spacja(text, lineLength)
    if x == -1:
        return text
    else:
        return text[:x] + '\n' + insertNewlines(text[x+1:], lineLength)

answered Mar 17, 2013 at 12:58

uselpa

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