Eryk Sun <[email protected]> added the comment:
> but I'm interrested in knowing more about the issue/original cause.
When the readline module is imported in interactive mode, the
PyOS_ReadlineFunctionPointer function pointer is set to call_readline(), which
uses GNU Readline. Otherwise PyOS_Readline() calls PyOS_StdioReadline(), which
calls my_fgets() and thus C standard I/O fgets().
In Linux, when the terminal is in canonical mode, a low-level read() is
buffered with a limit of 4096 bytes. If the limit is exceeded, the call returns
just the first 4095 bytes plus a trailing newline. You can verify this with
os.read(0, 5000). GNU Readline disables canonical mode and works with the
terminal at a lower level. I am far from an expert with Unix terminals, but
here's the basics of something that allows input() to read more than 4096
characters without having to import the readline module.
import sys
import termios
LFLAG = 3
settings = termios.tcgetattr(sys.stdin.fileno())
settings[LFLAG] &= ~termios.ICANON
termios.tcsetattr(sys.stdin.fileno(), termios.TCSANOW, settings)
try:
s = input()
finally:
settings[LFLAG] |= termios.ICANON
termios.tcsetattr(sys.stdin.fileno(), termios.TCSANOW, settings)
print(len(s))
----------
nosy: +eryksun
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<https://bugs.python.org/issue45511>
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