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POUsing Python codecs causes readline problems with sys.stdin?
 

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    <p>I am writing a Python wrapper script (childscript.py) for a command line executable (childprogram). Another executable, (parentprogram) spawns childscript.py and pipes output into childscript.py. childscript.py spawns childprogram with:</p> <pre><code> retval = subprocess.Popen(RUNLINE, shell=False, stdout=None, stderr=None, stdin=subprocess.PIPE) </code></pre> <p>If childscript.py does a series of reads from sys.stdin straight up using readline:</p> <pre><code>line = sys.stdin.readline() </code></pre> <p>I am able to get all the output from parentprogram and feed it into childprogram.</p> <p>However, if I try to use the codecs module by doing:</p> <pre><code>sys.stdin = codecs.open(sys.stdin.fileno(), encoding='iso-8859-1', mode='rb', buffering=0) </code></pre> <p>or do a:</p> <pre><code>sys.stdin = codecs.getreader('iso-8859-1')(sys.stdin.detach()) </code></pre> <p>and attempt to do the read, the read does not get all the output from parentprogram. If I force additional output from parentprogram, the missing bits come out along with part of the additional output that I pushed in. It looks like childscript.py is not reading everything that it is being provided to it when I use the codecs module.</p> <p>Am I doing something totally wrong? Without the codecs, childscript.py triggers an exception when presented with iso-8859-1 encoded stuff from parentprogram.</p> <p>EDIT:<br> I discovered that Python v3.x "open" can take the encoding option as well. I changed the line to use "open" instead of "codecs.open":</p> <pre><code> sys.stdin = open(sys.stdin.fileno(), encoding='iso-8859-1', mode='r') </code></pre> <p>and it works as expected, without any of the problems that open.codecs produces. I've switched my script to use "open" instead.</p> <p>If anybody can explain why the codecs module behaves differently, I'd appreciate it.</p>
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