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88 lines
3.2 KiB
Python
88 lines
3.2 KiB
Python
from __future__ import annotations
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import errno
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import os
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import sys
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from contextlib import contextmanager
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from typing import IO, Iterator, TextIO
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__all__ = ["flush_stdout"]
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def flush_stdout(stdout: TextIO, data: str) -> None:
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# If the IO object has an `encoding` and `buffer` attribute, it means that
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# we can access the underlying BinaryIO object and write into it in binary
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# mode. This is preferred if possible.
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# NOTE: When used in a Jupyter notebook, don't write binary.
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# `ipykernel.iostream.OutStream` has an `encoding` attribute, but not
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# a `buffer` attribute, so we can't write binary in it.
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has_binary_io = hasattr(stdout, "encoding") and hasattr(stdout, "buffer")
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try:
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# Ensure that `stdout` is made blocking when writing into it.
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# Otherwise, when uvloop is activated (which makes stdout
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# non-blocking), and we write big amounts of text, then we get a
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# `BlockingIOError` here.
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with _blocking_io(stdout):
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# (We try to encode ourself, because that way we can replace
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# characters that don't exist in the character set, avoiding
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# UnicodeEncodeError crashes. E.g. u'\xb7' does not appear in 'ascii'.)
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# My Arch Linux installation of july 2015 reported 'ANSI_X3.4-1968'
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# for sys.stdout.encoding in xterm.
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if has_binary_io:
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stdout.buffer.write(data.encode(stdout.encoding or "utf-8", "replace"))
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else:
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stdout.write(data)
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stdout.flush()
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except OSError as e:
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if e.args and e.args[0] == errno.EINTR:
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# Interrupted system call. Can happen in case of a window
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# resize signal. (Just ignore. The resize handler will render
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# again anyway.)
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pass
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elif e.args and e.args[0] == 0:
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# This can happen when there is a lot of output and the user
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# sends a KeyboardInterrupt by pressing Control-C. E.g. in
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# a Python REPL when we execute "while True: print('test')".
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# (The `ptpython` REPL uses this `Output` class instead of
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# `stdout` directly -- in order to be network transparent.)
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# So, just ignore.
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pass
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else:
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raise
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@contextmanager
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def _blocking_io(io: IO[str]) -> Iterator[None]:
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"""
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Ensure that the FD for `io` is set to blocking in here.
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"""
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if sys.platform == "win32":
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# On Windows, the `os` module doesn't have a `get/set_blocking`
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# function.
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yield
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return
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try:
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fd = io.fileno()
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blocking = os.get_blocking(fd)
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except: # noqa
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# Failed somewhere.
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# `get_blocking` can raise `OSError`.
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# The io object can raise `AttributeError` when no `fileno()` method is
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# present if we're not a real file object.
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blocking = True # Assume we're good, and don't do anything.
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try:
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# Make blocking if we weren't blocking yet.
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if not blocking:
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os.set_blocking(fd, True)
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yield
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finally:
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# Restore original blocking mode.
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if not blocking:
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os.set_blocking(fd, blocking)
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