Formatting line breaks in python strings

Question

I have a string:

f = open("file.txt", r)
message = f.read()

print message
>>> "To: email\ntitle: add title here\nDescription: whatever here\n"

I can split the string by doing:

f_email, f_title, f_description, blank = message.split('\n')

But the problem arises when I have the message like this:

"To: email\ntitle: add title here\nDescription: first line\nSecond line\nthirdline\n"

When I split the string it splits the description as well. I have tried:

f_email, f_title, f_description, blank = message.split('\n',4)

But that obviously returns ValueError because it is splitting more 4 \n's.

Any suggestions?

If the 'To' and 'title' are always on their own line with no internal linebreaks, you could just split on \n, where the first element is email, second title, and do '\n'.join( therest ) for the body? — mathematical.coffee
– mathematical.coffee, Commented Apr 18, 2012 at 13:42

Hooked · Accepted Answer · 2012-04-18 13:41:23Z

4

When you run .split('\n') you return a list. Rather than assign the variables when you split, you can pull them out of the list:

tokens = message.split('\n')
f_email = tokens[0]
f_title = tokens[1]
f_description = tokens[2]

This can be made less fragile by checking the size of the list. If you know it needs at least three elements, you can:

assert(len(tokens)>=3)

Another way to get around this is to wrap the thing up in a try/except block:

tokens = message.split('\n')
try:  
    f_description = tokens[2]
except:
    f_description = None

That way you can handle the case for a shorter list the exact way you like!

answered Apr 18, 2012 at 13:41

Hooked

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Comments

Rafal R · Accepted Answer · 2012-04-18 13:45:17Z

4

@Hooked gave a good answer for Python2. Since in Python3 * works also for tuple unpacking, you can do:

f_email, f_title, *f_description = tokens

The details are in PEP 3132

answered Apr 18, 2012 at 13:45

Rafal R

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3 Comments

Gareth Latty Over a year ago

Arg, I was just about to post this ;) +1, it's the nice solution for 3.x users.

covertCoder Over a year ago

for completeness, you can join the elements of f_description with '\n's to regain the original description string.

Rafal R Over a year ago

Also, the solution in this spirit, can be adapted to Python2, by passing *tokens to a method which does the processing.

Gareth Latty · Accepted Answer · 2012-04-18 13:48:54Z

1

If you don't want to use the text as a whole, and are not under 3.x to use the nice splat unpacking, you can simply do it like this:

email = None
title = None
description = ""
with open("test.txt", "r") as f:
    for number, line in enumerate(f):
       if number == 0:
           email = line.strip()
       elif number == 1:
           title = line.strip()
       else:
           description += line

answered Apr 18, 2012 at 13:48

Gareth Latty

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1 Comment

Neeran Over a year ago

+1: Thank you very helpful but the code can look a bit long if I have a very long string from a file.

Gergely Sipkai · Accepted Answer · 2012-04-18 14:27:37Z

1

When you use message.split('\n', 2) you get three parts: first line, second line and remaining lines in one.

Use this form:

f = open("file.txt")  
f_email, f_title, f_description = f.read.split('\n', 2)  
f.close()

Or this:

f = open("file.txt")  
f_email = f.readline()  
f_title = f.readline()  
f_description = f.read()  
f.close()

answered Apr 18, 2012 at 14:27

Gergely Sipkai

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