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POHow do I handle Python unicode strings with null-bytes the 'right' way?
 

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  1. POHow do I handle Python unicode strings with null-bytes the 'right' way?
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    <p><strong>Question</strong></p> <p>It seems that PyWin32 is comfortable with giving null-terminated unicode strings as return values. I would like to deal with these strings the 'right' way.</p> <p>Let's say I'm getting a string like: <code>u'C:\\Users\\Guest\\MyFile.asy\x00\x00sy'</code>. This appears to be a C-style null-terminated string hanging out in a Python unicode object. I want to trim this bad boy down to a regular ol' string of characters that I could, for example, display in a window title bar.</p> <p>Is trimming the string off at the first null byte the right way to deal with it?</p> <p>I didn't expect to get a return value like this, so I wonder if I'm missing something important about how Python, Win32, and unicode play together... or if this is just a PyWin32 bug.</p> <p><strong>Background</strong></p> <p>I'm using the Win32 file chooser function <a href="http://docs.activestate.com/activepython/2.7/pywin32/win32gui__GetSaveFileNameW_meth.html" rel="nofollow"><code>GetOpenFileNameW</code></a> from the PyWin32 package. According to the documentation, this function returns a tuple containing the full filename path as a Python unicode object.</p> <p>When I open the dialog with an existing path and filename set, I get a strange return value. </p> <p>For example I had the default set to: <code>C:\\Users\\Guest\\MyFileIsReallyReallyReallyAwesome.asy</code></p> <p>In the dialog I changed the name to <code>MyFile.asy</code> and clicked save.</p> <p>The full path part of the return value was: u'C:\Users\Guest\MyFile.asy\x00wesome.asy'`</p> <p>I expected it to be: <code>u'C:\\Users\\Guest\\MyFile.asy'</code></p> <p>The function is returning a recycled buffer without trimming off the terminating bytes. Needless to say, the rest of my code wasn't set up for handling a C-style null-terminated string.</p> <p><strong>Demo Code</strong></p> <p>The following code demonstrates null-terminated string in return value from GetSaveFileNameW.</p> <p>Directions: In the dialog change the filename to 'MyFile.asy' then click Save. Observe what is printed to the console. The output I get is <code>u'C:\\Users\\Guest\\MyFile.asy\x00wesome.asy'</code>.</p> <pre><code>import win32gui, win32con if __name__ == "__main__": initial_dir = 'C:\\Users\\Guest' initial_file = 'MyFileIsReallyReallyReallyAwesome.asy' filter_string = 'All Files\0*.*\0' (filename, customfilter, flags) = \ win32gui.GetSaveFileNameW(InitialDir=initial_dir, Flags=win32con.OFN_EXPLORER, File=initial_file, DefExt='txt', Title="Save As", Filter=filter_string, FilterIndex=0) print repr(filename) </code></pre> <p>Note: If you don't shorten the filename enough (for example, if you try MyFileIsReally.asy) the string will be complete without a null byte.</p> <p><strong>Environment</strong></p> <p>Windows 7 Professional 64-bit (no service pack), Python 2.7.1, PyWin32 Build 216</p> <p><strong>UPDATE: PyWin32 Tracker Artifact</strong></p> <p>Based on the comments and answers I have received so far, this is likely a pywin32 bug so I filed a <a href="https://sourceforge.net/tracker/?func=detail&amp;aid=3277647&amp;group_id=78018&amp;atid=551954" rel="nofollow">tracker artifact</a>.</p> <p><strong>UPDATE 2: Fixed!</strong></p> <p>Mark Hammond reported in the tracker artifact that this is indeed a bug. A fix was checked in to rev f3fdaae5e93d, so hopefully that will make the next release.</p> <p>I think Aleksi Torhamo's answer below is the best solution for versions of PyWin32 before the fix.</p>
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    1. CO+1 Huh, seems like you found a PyWin32 bug!
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    2. COI have dropped Mark Hammond (the primary PyWin32 maintainer) a quick note referring him to this page.
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    3. CO@Tom Thanks! I also filed a tracker artifact here: https://sourceforge.net/tracker/?func=detail&aid=3277647&group_id=78018&atid=551954
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