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