newby question: Splitting a string - separator

[Thomas Liesner]

Hi all,

i am having a textfile which contains a single string with names.
I want to split this string into its records an put them into a list.
In "normal" cases i would do something like:

#!/usr/bin/python
inp = open("file")
data = inp.read()
names = data.split()
inp.close()

The problem is, that the names contain spaces an the records are also
just seprarated by spaces. The only thing i can rely on, ist that the
recordseparator is always more than a single whitespace.

I thought of something like defining the separator for split() by using
a regex for "more than one whitespace". RegEx for whitespace is \s, but
what would i use for "more than one"? \s+?

TIA,
Tom

[Steven D'Aprano]

On Fri, 09 Dec 2005 18:02:02 -0800, James Stroud wrote:

Thomas Liesner wrote:

Hi all,

i am having a textfile which contains a single string with names.
I want to split this string into its records an put them into a list.
In "normal" cases i would do something like:

#!/usr/bin/python
inp = open("file")
data = inp.read()
names = data.split()
inp.close( )

The problem is, that the names contain spaces an the records are also
just seprarated by spaces. The only thing i can rely on, ist that the
recordseparator is always more than a single whitespace.

I thought of something like defining the separator for split() by using
a regex for "more than one whitespace". RegEx for whitespace is \s, but
what would i use for "more than one"? \s+?

TIA,
Tom

The one I like best goes like this:

py> data = "Guido van Rossum Tim Peters Thomas Liesner"
py> names = [n for n in data.split() if n]
py> names
['Guido', 'van', 'Rossum', 'Tim', 'Peters', 'Thomas', 'Liesner']

I think it is theoretically faster (and more pythonic) than using regexes.

Yes, but the correct result would be:

['Guido van Rossum', 'Tim Peters', 'Thomas Liesner']

Your code is short, elegant but wrong.

It could also be shorter and more elegant:

# your version
py> data = "Guido van Rossum Tim Peters Thomas Liesner"
py> [n for n in data.split() if n]
['Guido', 'van', 'Rossum', 'Tim', 'Peters', 'Thomas', 'Liesner']

# my version
py> data = "Guido van Rossum Tim Peters Thomas Liesner"
py> data.split()
['Guido', 'van', 'Rossum', 'Tim', 'Peters', 'Thomas', 'Liesner']

The "if n" in the list comp is superfluous, and without that, the whole
list comp is unnecessary.

--
Steven.

[James Stroud]

Steven D'Aprano wrote:

On Fri, 09 Dec 2005 18:02:02 -0800, James Stroud wrote:

Thomas Liesner wrote:

Hi all,

i am having a textfile which contains a single string with names.
I want to split this string into its records an put them into a list.
In "normal" cases i would do something like:

#!/usr/bin/python
inp = open("file")
data = inp.read()
names = data.split()
inp.close ()
The problem is, that the names contain spaces an the records are also
just seprarated by spaces. The only thing i can rely on, ist that the
recordsepara tor is always more than a single whitespace.

I thought of something like defining the separator for split() by using
a regex for "more than one whitespace". RegEx for whitespace is \s, but
what would i use for "more than one"? \s+?

TIA,
Tom

The one I like best goes like this:

py> data = "Guido van Rossum Tim Peters Thomas Liesner"
py> names = [n for n in data.split() if n]
py> names
['Guido', 'van', 'Rossum', 'Tim', 'Peters', 'Thomas', 'Liesner']

I think it is theoretically faster (and more pythonic) than using regexes.

Yes, but the correct result would be:

['Guido van Rossum', 'Tim Peters', 'Thomas Liesner']

Your code is short, elegant but wrong.

It could also be shorter and more elegant:

# your version
py> data = "Guido van Rossum Tim Peters Thomas Liesner"
py> [n for n in data.split() if n]
['Guido', 'van', 'Rossum', 'Tim', 'Peters', 'Thomas', 'Liesner']

# my version
py> data = "Guido van Rossum Tim Peters Thomas Liesner"
py> data.split()
['Guido', 'van', 'Rossum', 'Tim', 'Peters', 'Thomas', 'Liesner']

The "if n" in the list comp is superfluous, and without that, the whole
list comp is unnecessary.

see my post from 1 hr before this one.

[Tim Roberts]

James Stroud <js*****@mbi.uc la.edu> wrote:

The one I like best goes like this:

py> data = "Guido van Rossum Tim Peters Thomas Liesner"
py> names = [n for n in data.split() if n]
py> names
['Guido', 'van', 'Rossum', 'Tim', 'Peters', 'Thomas', 'Liesner']

I think it is theoretically faster (and more pythonic) than using regexes.

But it is slower than this, which produces EXACTLY the same (incorrect)
result:

data = "Guido van Rossum Tim Peters Thomas Liesner"
names = data.split()
--
- Tim Roberts, ti**@probo.com
Providenza & Boekelheide, Inc.

[Fredrik Lundh]

James Stroud wrote:

py> data = "Guido van Rossum Tim Peters Thomas Liesner"
py> names = [n for n in data.split() if n]
py> names
['Guido', 'van', 'Rossum', 'Tim', 'Peters', 'Thomas', 'Liesner']

I think it is theoretically faster (and more pythonic) than using
regexes.

Unfortunately it gives the wrong result.

Just an example. Here is the "correct version":

names = [n for n in data.split(" ") if n]

where "correct" is "still wrong", and "theoretica lly faster" means "slightly
slower" (at least if fix your version, and precompile the pattern).

</F>