Preview: base_futures.py
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/lib64/python3.9/asyncio/base_futures.py
__all__ = ()
import reprlib
from _thread import get_ident
from . import format_helpers
# States for Future.
_PENDING = 'PENDING'
_CANCELLED = 'CANCELLED'
_FINISHED = 'FINISHED'
def isfuture(obj):
"""Check for a Future.
This returns True when obj is a Future instance or is advertising
itself as duck-type compatible by setting _asyncio_future_blocking.
See comment in Future for more details.
"""
return (hasattr(obj.__class__, '_asyncio_future_blocking') and
obj._asyncio_future_blocking is not None)
def _format_callbacks(cb):
"""helper function for Future.__repr__"""
size = len(cb)
if not size:
cb = ''
def format_cb(callback):
return format_helpers._format_callback_source(callback, ())
if size == 1:
cb = format_cb(cb[0][0])
elif size == 2:
cb = '{}, {}'.format(format_cb(cb[0][0]), format_cb(cb[1][0]))
elif size > 2:
cb = '{}, <{} more>, {}'.format(format_cb(cb[0][0]),
size - 2,
format_cb(cb[-1][0]))
return f'cb=[{cb}]'
# bpo-42183: _repr_running is needed for repr protection
# when a Future or Task result contains itself directly or indirectly.
# The logic is borrowed from @reprlib.recursive_repr decorator.
# Unfortunately, the direct decorator usage is impossible because of
# AttributeError: '_asyncio.Task' object has no attribute '__module__' error.
#
# After fixing this thing we can return to the decorator based approach.
_repr_running = set()
def _future_repr_info(future):
# (Future) -> str
"""helper function for Future.__repr__"""
info = [future._state.lower()]
if future._state == _FINISHED:
if future._exception is not None:
info.append(f'exception={future._exception!r}')
else:
key = id(future), get_ident()
if key in _repr_running:
result = '...'
else:
_repr_running.add(key)
try:
# use reprlib to limit the length of the output, especially
# for very long strings
result = reprlib.repr(future._result)
finally:
_repr_running.discard(key)
info.append(f'result={result}')
if future._callbacks:
info.append(_format_callbacks(future._callbacks))
if future._source_traceback:
frame = future._source_traceback[-1]
info.append(f'created at {frame[0]}:{frame[1]}')
return info
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