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:
[color=blue]
> #!/usr/bin/python
> inp = open("file")
> data = inp.read()
> names = data.split()
> inp.close()[/color]

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

[Michael Spencer]

Re: newby question: Splitting a string - separator

Thomas Liesner wrote:[color=blue]
> 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:
>[color=green]
>> #!/usr/bin/python
>> inp = open("file")
>> data = inp.read()
>> names = data.split()
>> inp.close()[/color]
>
> 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[/color]
\s+ gives one or more, you need \s{2,} for two or more:
[color=blue][color=green][color=darkred]
>>> import re
>>> re.split("\s{2, }","Guido van Rossum Tim Peters Thomas Liesner")[/color][/color][/color]
['Guido van Rossum', 'Tim Peters', 'Thomas Liesner'][color=blue][color=green][color=darkred]
>>>[/color][/color][/color]

Michael

[Noah]

Re: newby question: Splitting a string - separator


Thomas Liesner wrote:[color=blue]
> ...
> 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+?[/color]

For your split regex you could say
"\s\s+"
or
"\s{2,}"

This should work for you:
YOUR_SPLIT_LIST = re.split("\s{2, }", YOUR_STRING)

Yours,
Noah

[Jim]

Re: newby question: Splitting a string - separator

Hi Tom,
[color=blue]
> a regex for "more than one whitespace". RegEx for whitespace is \s, but
> what would i use for "more than one"? \s+?[/color]

For more than one, I'd use

\s\s+

-Jim

[James Stroud]

Re: newby question: Splitting a string - separator

Thomas Liesner wrote:[color=blue]
> 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:
>
>[color=green]
>>#!/usr/bin/python
>>inp = open("file")
>>data = inp.read()
>>names = data.split()
>>inp.close()[/color]
>
>
> 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[/color]

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.

James

[Kent Johnson]

Re: newby question: Splitting a string - separator

James Stroud wrote:[color=blue]
> 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.[/color]

Unfortunately it gives the wrong result.

Kent

[Tim Peters]

Re: newby question: Splitting a string - separator

[James Stroud][color=blue][color=green]
>> 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.[/color][/color]

[Kent Johnson][color=blue]
> Unfortunately it gives the wrong result.[/color]

Still, it gets extra points for being such a pleasing example ;-)

[bonono@gmail.com]

Re: newby question: Splitting a string - separator


Thomas Liesner wrote:[color=blue]
> 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:
>[color=green]
> > #!/usr/bin/python
> > inp = open("file")
> > data = inp.read()
> > names = data.split()
> > inp.close()[/color]
>
> 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+?
>[/color]
Can I just use "two space" as the seperator ?

[ x.strip() for x in data.split(" ") ]

[James Stroud]

Re: newby question: Splitting a string - separator

Kent Johnson wrote:[color=blue]
> James Stroud wrote:
>[color=green]
>> 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.[/color]
>
>
> Unfortunately it gives the wrong result.
>
> Kent[/color]

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


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

James

[Michael Spencer]

Re: newby question: Splitting a string - separator

bonono@gmail.co m wrote:[color=blue]
> Thomas Liesner wrote:[color=green]
>> 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:
>>[color=darkred]
>>> #!/usr/bin/python
>>> inp = open("file")
>>> data = inp.read()
>>> names = data.split()
>>> inp.close()[/color]
>> 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+?
>>[/color]
> Can I just use "two space" as the seperator ?
>
> [ x.strip() for x in data.split(" ") ]
>[/color]
If you like, but it will create dummy entries if there are more than two spaces:
[color=blue][color=green][color=darkred]
>>> data = "Guido van Rossum Tim Peters Thomas Liesner"
>>> [ x.strip() for x in data.split(" ") ][/color][/color][/color]
['Guido van Rossum', 'Tim Peters', '', 'Thomas Liesner']

You could add a condition to the listcomp:
[color=blue][color=green][color=darkred]
>>> [name.strip() for name in data.split(" ") if name][/color][/color][/color]
['Guido van Rossum', 'Tim Peters', 'Thomas Liesner']

but what if there is some other whitespace character?
[color=blue][color=green][color=darkred]
>>> data = "Guido van Rossum Tim Peters \t Thomas Liesner"
>>> [name.strip() for name in data.split(" ") if name][/color][/color][/color]
['Guido van Rossum', 'Tim Peters', '', 'Thomas Liesner'][color=blue][color=green][color=darkred]
>>>[/color][/color][/color]

perhaps a smarter condition?
[color=blue][color=green][color=darkred]
>>> [name.strip() for name in data.split(" ") if name.strip(" \t")][/color][/color][/color]
['Guido van Rossum', 'Tim Peters', 'Thomas Liesner']

but this is beginning to feel like hard work.


I think this is a case where it's not worth the effort to try to avoid the regexp
[color=blue][color=green][color=darkred]
>>> import re
>>> re.split("\s{2, }",data)[/color][/color][/color]
['Guido van Rossum', 'Tim Peters', 'Thomas Liesner'][color=blue][color=green][color=darkred]
>>>[/color][/color][/color]

Michael

[Steven D'Aprano]

Re: newby question: Splitting a string - separator

On Fri, 09 Dec 2005 18:02:02 -0800, James Stroud wrote:
[color=blue]
> Thomas Liesner wrote:[color=green]
>> 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:
>>
>>[color=darkred]
>>>#!/usr/bin/python
>>>inp = open("file")
>>>data = inp.read()
>>>names = data.split()
>>>inp.close( )[/color]
>>
>>
>> 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[/color]
>
> 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.[/color]


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]

Re: newby question: Splitting a string - separator

Steven D'Aprano wrote:[color=blue]
> On Fri, 09 Dec 2005 18:02:02 -0800, James Stroud wrote:
>
>[color=green]
>>Thomas Liesner wrote:
>>[color=darkred]
>>>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[/color]
>>
>>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.[/color]
>
>
>
> 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.
>
>
>[/color]
see my post from 1 hr before this one.

[Tim Roberts]

Re: newby question: Splitting a string - separator

James Stroud <jstroud@mbi.uc la.edu> wrote:[color=blue]
>
>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.[/color]

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, timr@probo.com
Providenza & Boekelheide, Inc.

[Fredrik Lundh]

Re: newby question: Splitting a string - separator

James Stroud wrote:
[color=blue][color=green][color=darkred]
> >> 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.[/color]
> >
> > Unfortunately it gives the wrong result.[/color]
>
> Just an example. Here is the "correct version":
>
> names = [n for n in data.split(" ") if n][/color]

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

</F>