CODEWITHSUNDEEP
python
Yeo
Yeo

Reputation: 11794

Force string to be one liner

Do anyone know an alternative ways to force a string into one liner? May be a python built-in method? or perhaps a better implementation (explain why)?

For example:

Hello World
Foo Bar

Become 

Hello World Foo Bar

Implementation

def strip_newline(s):
    return ' '.join(mystring.splitlines())

strip_newline = lambda _: ' '.join(_.splitlines())

Extra Note:

For those who reminds me about character replacement of \n, a line character into . The drawback is you need to watch out for \r, carriage return character too. :-)

Thus you need to do mystring.replace('\r', ' ').replace('\n', ' ').

Upvotes: 2

Views: 205

Answers (3)

Iron Fist
Iron Fist

Reputation: 10951

Other approach would be using str.translate method, by building the dictionary of translation (char_to_remove:None mapping) then applying it through str.translate :

>>> import string
>>> string.whitespace
' \t\n\r\x0b\x0c'
>>> st
'\n1\n2\n3\n4\n5\n'
>>>
>>> dws = dict.fromkeys(ord(c) for c in string.whitespace)
>>> 
>>> dws
{32: None, 9: None, 10: None, 11: None, 12: None, 13: None}
>>> 
>>> st.translate(dws)
'12345'

Of course, this would remove the white space within your string, you can skip this case by conditional comprehension:

>>> dws = dict.fromkeys(ord(c) for c in string.whitespace if c != ' ')

Or simply:

>>> import os
>>> os.linesep
'\n' #on my ubuntu box
>>> st.translate({ord(os.linesep):None})
'12345'

Upvotes: 0

Jacob Ritchie
Jacob Ritchie

Reputation: 1401

Performance

I timed both methods in a bash shell, and it appears that the simple 

stri.replace("\n", " ")

is faster than your proposed solution.

(The file hello.txt is a file containing 1000 lines with the phrase "Hello World".)

~$ time python -c 'f = open("hello.txt","r"); stri = f.read(); stri.replace("\n", " ")'

real    0m0.130s
user    0m0.021s
sys     0m0.023s

~$ time python -c 'f = open("hello.txt","r"); stri = f.read(); " ".join(stri.splitlines())'

real    0m0.317s
user    0m0.032s
sys     0m0.028s

Alternatively, if you use the readlines() method instead of the read() method, you can remove the need for your call to splitlines() and gain some performance improvement there.

~$ time python -c 'f = open("hello.txt","r"); stri = f.readlines(); " ".join(stri)'

real    0m0.176s
user    0m0.033s
sys     0m0.026s

Line Endings

I'm using linux, so I don't have to worry about the \r character. However, in your case, Windows line endings are always of the form \r\n, so you can replace your two calls to the replace() method 

stri.replace("\r", " ").replace("\n", " ")

with a single call:

stri.replace("\r\n", " ")

which should also improve performance.

Upvotes: 2

max
max

Reputation: 2817

I think simple replace would be the fastest method:

s = '''
1
2
3
4
5
'''

print (s.replace("\n", " "))

Upvotes: 3

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