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How to split with "\" character, and licence copyleft mirror of ©

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  How to split with "\" character, and licence copyleft mirror of © materile11@gmail.com - 2013-09-01 17:03 -0700
    Re: How to split with "\" character, and licence copyleft mirror of © Cameron Simpson <cs@zip.com.au> - 2013-09-02 10:23 +1000
    Re: How to split with "\" character, and licence copyleft mirror of © Tim Chase <python.list@tim.thechases.com> - 2013-09-01 19:34 -0500
      Re: How to split with "\" character, and licence copyleft mirror of © materile11@gmail.com - 2013-09-01 21:20 -0700
    Re: How to split with "\" character, and licence copyleft mirror of © Tim Chase <python.list@tim.thechases.com> - 2013-09-01 19:40 -0500
    Re: How to split with "\" character, and licence copyleft mirror of © Tim Roberts <timr@probo.com> - 2013-09-01 19:40 -0700
      Re: How to split with "\" character, and licence copyleft mirror of © Ethan Furman <ethan@stoneleaf.us> - 2013-09-02 13:22 -0700
        Re: How to split with "\" character, and licence copyleft mirror of © Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-09-03 02:06 +0000
          Re: How to split with "\" character, and licence copyleft mirror of © Tim Chase <python.list@tim.thechases.com> - 2013-09-03 05:31 -0500
          Re: How to split with "\" character, and licence copyleft mirror of © random832@fastmail.us - 2013-09-03 14:31 -0400
            Re: How to split with "\" character, and licence copyleft mirror of © Tim Roberts <timr@probo.com> - 2013-09-05 20:33 -0700
              Re: How to split with "\" character, and licence copyleft mirror of � Terry Reedy <tjreedy@udel.edu> - 2013-09-06 02:15 -0400
              Re: How to split with "\" character, and licence copyleft mirror of © random832@fastmail.us - 2013-09-06 09:29 -0400
              Re: How to split with "\" character, and licence copyleft mirror of � Fábio Santos <fabiosantosart@gmail.com> - 2013-09-11 11:16 +0100

#53441 — How to split with "\" character, and licence copyleft mirror of ©

Hello everybody
I'm trying to run this: 

<code>
>>> a = 'E:\Dropbox\jjfsdjjsdklfj\sdfjksdfkjslkj\flute.wav'
>>> a.split('\')

SyntaxError: EOL while scanning string literal
</code>

I think that the character '\' is the problem, but unfortunately I'm developing a small app for windows and I need to show only the name of the .wav file, in this case 'flute.wav'.

I also want to know how to mirror a character, in my case this one ©, because I'll use the Copyleft http://en.wikipedia.org/wiki/Copyleft to distribute my app.

Thanks.

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#53442

On 01Sep2013 17:03, materile11@gmail.com <materile11@gmail.com> wrote:
| <code>
| >>> a = 'E:\Dropbox\jjfsdjjsdklfj\sdfjksdfkjslkj\flute.wav'
| >>> a.split('\')
| SyntaxError: EOL while scanning string literal
| </code>
| 
| I think that the character '\' is the problem, but unfortunately I'm developing a small app for windows and I need to show only the name of the .wav file, in this case 'flute.wav'.

Firstly, you want to say '\\' for a slosh (just as you would say '\n' for a linefeed).

However, you really should use the os.path module, in particular os.path.split().

Have a read of:
  http://docs.python.org/3/library/os.path.html#module-os.path
  http://docs.python.org/2/library/os.path.html#module-os.path

| I also want to know how to mirror a character, in my case this
| one ©, because I'll use the Copyleft http://en.wikipedia.org/wiki/Copyleft
| to distribute my app.

Isn't that a copyright symbol? I'd have a look at the "uncidoedata" module,
myself.

Cheers,
-- 
Cameron Simpson <cs@zip.com.au>

Just because Unix is a multiuser system doesn't mean I want to share it with
anybody!        - Paul Tomblin, in rec.aviation.military

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#53443

On 2013-09-01 17:03, materile11@gmail.com wrote:
> Hello everybody
> I'm trying to run this: 
> 
> <code>
> >>> a = 'E:\Dropbox\jjfsdjjsdklfj\sdfjksdfkjslkj\flute.wav'
> >>> a.split('\')
> 
> SyntaxError: EOL while scanning string literal
> </code>
> 
> I think that the character '\' is the problem, but unfortunately
> I'm developing a small app for windows and I need to show only the
> name of the .wav file, in this case 'flute.wav'.

To directly answer your question, you need to escape the "\" so it's

  a.split('\\')

That said, it's far better to use Python's built-ins to do the
processing for you:

  >>> import os
  >>> print os.path.basename(a)
  flute.wav

which does what you want *and* works cross-platform:

  [on Linux]
  >>> a = '/home/tkc/path/to/flute.wav'
  >>> print os.path.basename(a)
  flute.wav

> I also want to know how to mirror a character, in my case this one
> ©, because I'll use the Copyleft

This can't be done in much of a general way:  Unicode doesn't specify
this character, and the URL you provided suggests combining two
Unicode characters to get ↄ⃝  Unfortunately, (1) it requires a
display that knows how to produce that, which many terminals can't;
and (2) it's purely visual, not semantic.  If that's what you really
want, you should be able to use:

  copyleft_symbol = u"\u2184\u20DD"

Just be aware that it may not always display the way you expect it to.

-tkc

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#53454

El domingo, 1 de septiembre de 2013 19:34:16 UTC-5, Tim Chase  escribió:
> On 2013-09-01 17:03, materile11@gmail.com wrote:
> 
> > Hello everybody
> 
> > I'm trying to run this: 
> 
> > 
> 
> > <code>
> 
> > >>> a = 'E:\Dropbox\jjfsdjjsdklfj\sdfjksdfkjslkj\flute.wav'
> 
> > >>> a.split('\')
> 
> > 
> 
> > SyntaxError: EOL while scanning string literal
> 
> > </code>
> 
> > 
> 
> > I think that the character '\' is the problem, but unfortunately
> 
> > I'm developing a small app for windows and I need to show only the
> 
> > name of the .wav file, in this case 'flute.wav'.
> 
> 
> 
> To directly answer your question, you need to escape the "\" so it's
> 
> 
> 
>   a.split('\\')
> 
> 
> 
> That said, it's far better to use Python's built-ins to do the
> 
> processing for you:
> 
> 
> 
>   >>> import os
> 
>   >>> print os.path.basename(a)
> 
>   flute.wav
> 
> 
> 
> which does what you want *and* works cross-platform:
> 
> 
> 
>   [on Linux]
> 
>   >>> a = '/home/tkc/path/to/flute.wav'
> 
>   >>> print os.path.basename(a)
> 
>   flute.wav
> 
> 
> 
> > I also want to know how to mirror a character, in my case this one
> 
> > ©, because I'll use the Copyleft
> 
> 
> 
> This can't be done in much of a general way:  Unicode doesn't specify
> 
> this character, and the URL you provided suggests combining two
> 
> Unicode characters to get ↄ⃝  Unfortunately, (1) it requires a
> 
> display that knows how to produce that, which many terminals can't;
> 
> and (2) it's purely visual, not semantic.  If that's what you really
> 
> want, you should be able to use:
> 
> 
> 
>   copyleft_symbol = u"\u2184\u20DD"
> 
> 
> 
> Just be aware that it may not always display the way you expect it to.
> 
> 
> 
> -tkc


Thank you, I've used the os.path.basename to solve my problem.
Regards.

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#53444

On 2013-09-02 10:23, Cameron Simpson wrote:
> | I also want to know how to mirror a character, in my case this
> | one ©, because I'll use the Copyleft
> http://en.wikipedia.org/wiki/Copyleft | to distribute my app.
> 
> Isn't that a copyright symbol? I'd have a look at the "uncidoedata"
> module, myself.

Thanks to his link (which would have been more helpful with the
URL fragment:

http://en.wikipedia.org/wiki/Copyleft#Symbol

), I suspect the he means that it should be "the mirror image of a
copyright symbol".

And that would be "unicodedata", not "uncidoedata" (I don't think
that was the reversing he was talking about ;-)

-tkc

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#53450

materile11@gmail.com wrote:

>Hello everybody
>I'm trying to run this: 
>
><code>
>>>> a = 'E:\Dropbox\jjfsdjjsdklfj\sdfjksdfkjslkj\flute.wav'
>>>> a.split('\')
>
>SyntaxError: EOL while scanning string literal
></code>
>
>I think that the character '\' is the problem, but unfortunately I'm
>developing a small app for windows and I need to show only the name
>of the .wav file, in this case 'flute.wav'.

I assume you know that backslash has a special meaning in string constants.
For example the string '\n\r' contains exactly two characters, and no
backslashes.

When you want to use an actual backslash in an ordinary string constant,
you have to double it.  So, you could have written your code as:
    a = 'E:\\Dropbox\\jjfsdjjsdklfj\\sdfjksdfkjslkj\\flute.wav'
    a.split('\\')

Another altrnative is to use "raw" strings, in which backslashes are not
interpreted:
    a = r'E:\Dropbox\jjfsdjjsdklfj\sdfjksdfkjslkj\flute.wav'
    a.split(r'\')

I assume your filename is actually input to your program, and not as a
constant in your code, so that may not be a problem.  However, there is an
API to do exactly what you're asking:

  >>> import os
  >>> a=r'E:\Dropbox\one\two\three\flute.wav'
  >>> os.path.split(a)
  ('E:\\Dropbox\\one\\two\\three', 'flute.wav')
  >>> os.path.split(a)[1]
  'flute.wav'
  >>>
  
>I also want to know how to mirror a character, in my case this one ©,
>because I'll use the Copyleft http://en.wikipedia.org/wiki/Copyleft
>to distribute my app.

You can't "mirror" a character.  That is an invented glyph that is not
present in Unicode.  Fortunately, the character doesn't have any legal
meaning, so you can just include explanatory text in your description that
identifies your license.
-- 
Tim Roberts, timr@probo.com
Providenza & Boekelheide, Inc.

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#53526

On 09/01/2013 07:40 PM, Tim Roberts wrote:
>
> Another altrnative is to use "raw" strings, in which backslashes are not
> interpreted:
>      a = r'E:\Dropbox\jjfsdjjsdklfj\sdfjksdfkjslkj\flute.wav'
>      a.split(r'\')

Not quite.

--> r'\'
   File "<stdin>", line 1
     r'\'
        ^
SyntaxError: EOL while scanning string literal

In a raw string, the backslash is buggy (IMNSHO) when it's the last character.  Given the above error, you might think 
that to get a single-quote in a string delimited by single-quotes that you would use r'\'', but no:

--> r'\''
"\\'"

you get a backslash and a single-quote.  And if you try to escape the backslash to get only one?

--> r'\\'
'\\\\'

You get two.  Grrrr.

--
~Ethan~

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#53551

On Mon, 02 Sep 2013 13:22:37 -0700, Ethan Furman wrote:

> In a raw string, the backslash is buggy (IMNSHO) when it's the last
> character.  Given the above error, you might think that to get a
> single-quote in a string delimited by single-quotes that you would use
> r'\'', but no:
> 
> --> r'\''
> "\\'"

You get exactly what you asked for. It's a raw string, right, so 
backslash has no special powers, and "backslash C" should give you 
exactly backslash followed by C, for any character C. Which is exactly 
what you do get. So that's working correctly, as far as it goes.


> you get a backslash and a single-quote.  And if you try to escape the
> backslash to get only one?
> 
> --> r'\\'
> '\\\\'
> 
> You get two.  Grrrr.

Again, working as expected. Since backslash has no special powers, if you 
enter a string with backslash backslash, you ought to get two 
backslashes. Just as you do.


The *real* mystery is how the first example r'\'' succeeds in the first 
place, and that gives you a clue as to why r'\' doesn't. The answer is 
discussed in this bug report:

http://bugs.python.org/issue1271


Summarising, the parser understands backslash as an escape character, and 
when it scans the string r'\'' the backslash escapes the inner quote, but 
then when Python generates the string it skips the backslash escape 
mechanism. Since the parser knows that backslash escapes, it fails to 
parse r'\' and you get a SyntaxError. If you stick stuff at the end of 
the line, you get the SyntaxError at another place:

py> s = r'\'[:] # and more
  File "<stdin>", line 1
    s = r'\'[:] # and more
                         ^
SyntaxError: EOL while scanning string literal



So the real bug is with the parser.

It is likely that nobody noticed this bug in the first place because the 
current behaviour doesn't matter for regexes, which is the primary 
purpose of raw strings. You can't end a regex with an unescaped 
backslash, so r'abc\'' is an illegal regex and it doesn't matter if you 
can't create it.


-- 
Steven

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#53562

On 2013-09-03 02:06, Steven D'Aprano wrote:
>> So the real bug is with the parser.
> 
> It is likely that nobody noticed this bug in the first place
> because the current behaviour doesn't matter for regexes, which is
> the primary purpose of raw strings. You can't end a regex with an
> unescaped backslash, so r'abc\'' is an illegal regex and it doesn't
> matter if you can't create it.

I'd contend that the two primary purposes of raw strings (this is
starting to sound like a Spanish Inquisition sketch) are regexes and
DOS/Win32 file path literals.  And I hit this trailing-backslash case
all the time, as Vim's path-completion defaults to putting the
trailing backslash at the end.  So I might be entering a literal like

  r"c:\win

and hit <tab> which expands to

  r"c:\Windows\

for which I then need to both remove the backslash and close the
quote.  If Python's parser just blithely ignored terminal
backslashes, I could just close the quote and get on with my day.

-tkc

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#53576

On Tue, Sep 3, 2013, at 6:31, Tim Chase wrote:
> I'd contend that the two primary purposes of raw strings (this is
> starting to sound like a Spanish Inquisition sketch) are regexes and
> DOS/Win32 file path literals.  And I hit this trailing-backslash case
> all the time, as Vim's path-completion defaults to putting the
> trailing backslash at the end.  So I might be entering a literal like
> 
>   r"c:\win
> 
> and hit <tab> which expands to
> 
>   r"c:\Windows\
> 
> for which I then need to both remove the backslash and close the
> quote.  If Python's parser just blithely ignored terminal
> backslashes, I could just close the quote and get on with my day.

Of course, in 99% of situations where you can use a windows pathname in
Python, you are free to use it with a forward slash instead of a
backslash. The fact that you're using vim's file completion, which
automatically normalizes the path separator, is why you're running into
this issue when other people may not.

Maybe enabling the 'shellslash' option (which changes it to use forward
slash) will help you, though you should be aware this also affects the
expansion of the % variable, even in the :! command, which can cause
problems with certain usage patterns.

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#53753

random832@fastmail.us wrote:
>
>Of course, in 99% of situations where you can use a windows pathname in
>Python, you are free to use it with a forward slash instead of a
>backslash.

This is actually worth repeating, because it's not well known.

ALL Windows APIs handle forward and backward slashes interchangably.  It is
only the command interpreter that requires the backslash.
-- 
Tim Roberts, timr@probo.com
Providenza & Boekelheide, Inc.

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#53766 — Re: How to split with "\" character, and licence copyleft mirror of �

On 9/5/2013 11:33 PM, Tim Roberts wrote:
> random832@fastmail.us wrote:
>>
>> Of course, in 99% of situations where you can use a windows pathname in
>> Python, you are free to use it with a forward slash instead of a
>> backslash.
>
> This is actually worth repeating, because it's not well known.
>
> ALL Windows APIs handle forward and backward slashes interchangably.  It is
> only the command interpreter that requires the backslash.

and only for the path the the command, when needed, and not for the 
arguments of the command. Example, in a python development directory

 > pcbuild\python_d tools/scripts/patchcheck.py

-- 
Terry Jan Reedy

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#53785

On Thu, Sep 5, 2013, at 23:33, Tim Roberts wrote:
> random832@fastmail.us wrote:
> >
> >Of course, in 99% of situations where you can use a windows pathname in
> >Python, you are free to use it with a forward slash instead of a
> >backslash.
> 
> This is actually worth repeating, because it's not well known.
> 
> ALL Windows APIs handle forward and backward slashes interchangably.  It
> is only the command interpreter that requires the backslash.

Technically, that's not strictly true. There are certain strings you can
open that will only work with backslashes, relating to device paths
and/or the magic \\?\ prefix that removes the PATH_MAX limit
(CreateFileW only). That was what I meant by 99%.

And many situations in the command interpreter that require a backslash
can be used with forward slash by surrounding the string in quotes,
which you need to do anyway when you have an arbitrary string that may
contain spaces.

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#53947 — Re: How to split with "\" character, and licence copyleft mirror of �

[Multipart message — attachments visible in raw view] — view raw

On 6 Sep 2013 07:18, "Terry Reedy" <tjreedy@udel.edu> wrote:
>
> On 9/5/2013 11:33 PM, Tim Roberts wrote:
>>
>> random832@fastmail.us wrote:
>>>
>>>
>>> Of course, in 99% of situations where you can use a windows pathname in
>>> Python, you are free to use it with a forward slash instead of a
>>> backslash.
>>
>>
>> This is actually worth repeating, because it's not well known.
>>
>> ALL Windows APIs handle forward and backward slashes interchangably.  It
is
>> only the command interpreter that requires the backslash.
>
>
> and only for the path the the command, when needed, and not for the
arguments of the command. Example, in a python development directory
>
> > pcbuild\python_d tools/scripts/patchcheck.py
>

Interesting. I was pretty sure that forward slashes were allowed in this
situation, just that tab completion didn't work unless you used backslashes.

Well, fortunately I'm not able to check that these days.

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