On 15/10/2010 20:28, Dan wrote:
I am writing a Windows program in Python 3.1.2 that reads binary data
from stdin. Whenever it hits a \x1a character, stdin goes EOF and no
more data can be read. A short program that exhibits this problem is:
#listing of main.pyw
import sys
def go():
bb=sys.stdin.buffer.raw.read(10000)
print(bb,file=sys.stderr)
sys.stderr.flush()
go()
go()
The program is run as "pythonw.exe main.pyw"
When fed with a block of bytes equivalent to "bytes(range(1,255))",
the following output is observed...
b'\x01\x02\x03\x04\x05\x06\x07\x08\t\n\x0b\x0c\r\x0e\x0f
\x10\x11\x12\x13\x14\x15\x16\x17\x18\x19'
b''
...and according to the documentation, the empty bytes object means
EOF.
I wrote an equivalent program in C++ using the win32 ReadFile() call,
and it read all 255 bytes just fine. What am I doing wrong with the
python code?
I am using Erlang to launch the Python program as a subprocess. The
Erlang fragment that launches this and sends the data is:
Port=open_port( {spawn_executable, "c:/Python31/pythonw.exe"},
[{args, ["c:/iotest/main.pyw"]}]),
Port ! {self(),{command,lists:seq(1,255)}},
By default, Python opens stdin in buffered text mode in which '\x1A'
marks the end of the text. Try adding the "-u" option ("unbuffered") to
Python's command line:
pythonw.exe -u main.pyw
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