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v0.5.1
https://github.com/python/cpython
Revision 4ddb2d73ac661af516a252fe697ec05e726b0f20 authored by Miss Islington (bot) on 04 September 2020, 22:30:21 UTC, committed by GitHub on 04 September 2020, 22:30:21 UTC
I added some information to the `Concurrency and Multithreading` section of the `Developing with asyncio` guide. This is all information that would have helped me when I started using asyncio. I incorrectly assumed that `loop.call_soon_threadsafe()` and `run_coroutine_threadsafe()` could be called from a thread in a process separate from the one that the event loop is running in. Explicitly stating that this will not work will probably help some people starting out with asyncio in the future. I also added references to some other functions that can be used for inter-process communication without blocking the event loop. The section already mentions running blocking code in a ThreadPoolExecutor, but I think listing these other options in this section will also be helpful. (cherry picked from commit c68c5af2dc5ada8875a662f2beaac6234eae2a5a) Co-authored-by: Roger Iyengar <ri@rogeriyengar.com>
1 parent e77547b
Tip revision: 4ddb2d73ac661af516a252fe697ec05e726b0f20 authored by Miss Islington (bot) on 04 September 2020, 22:30:21 UTC
[3.8] Improve asyncio-dev 'Concurrency and Multithreading' docs (GH-20882) (GH-22010)
[3.8] Improve asyncio-dev 'Concurrency and Multithreading' docs (GH-20882) (GH-22010)
Tip revision: 4ddb2d7
linecache.py
"""Cache lines from Python source files.
This is intended to read lines from modules imported -- hence if a filename
is not found, it will look down the module search path for a file by
that name.
"""
import functools
import sys
import os
import tokenize
__all__ = ["getline", "clearcache", "checkcache"]
def getline(filename, lineno, module_globals=None):
lines = getlines(filename, module_globals)
if 1 <= lineno <= len(lines):
return lines[lineno-1]
else:
return ''
# The cache
# The cache. Maps filenames to either a thunk which will provide source code,
# or a tuple (size, mtime, lines, fullname) once loaded.
cache = {}
def clearcache():
"""Clear the cache entirely."""
global cache
cache = {}
def getlines(filename, module_globals=None):
"""Get the lines for a Python source file from the cache.
Update the cache if it doesn't contain an entry for this file already."""
if filename in cache:
entry = cache[filename]
if len(entry) != 1:
return cache[filename][2]
try:
return updatecache(filename, module_globals)
except MemoryError:
clearcache()
return []
def checkcache(filename=None):
"""Discard cache entries that are out of date.
(This is not checked upon each call!)"""
if filename is None:
filenames = list(cache.keys())
else:
if filename in cache:
filenames = [filename]
else:
return
for filename in filenames:
entry = cache[filename]
if len(entry) == 1:
# lazy cache entry, leave it lazy.
continue
size, mtime, lines, fullname = entry
if mtime is None:
continue # no-op for files loaded via a __loader__
try:
stat = os.stat(fullname)
except OSError:
cache.pop(filename, None)
continue
if size != stat.st_size or mtime != stat.st_mtime:
cache.pop(filename, None)
def updatecache(filename, module_globals=None):
"""Update a cache entry and return its list of lines.
If something's wrong, print a message, discard the cache entry,
and return an empty list."""
if filename in cache:
if len(cache[filename]) != 1:
cache.pop(filename, None)
if not filename or (filename.startswith('<') and filename.endswith('>')):
return []
fullname = filename
try:
stat = os.stat(fullname)
except OSError:
basename = filename
# Realise a lazy loader based lookup if there is one
# otherwise try to lookup right now.
if lazycache(filename, module_globals):
try:
data = cache[filename][0]()
except (ImportError, OSError):
pass
else:
if data is None:
# No luck, the PEP302 loader cannot find the source
# for this module.
return []
cache[filename] = (
len(data), None,
[line+'\n' for line in data.splitlines()], fullname
)
return cache[filename][2]
# Try looking through the module search path, which is only useful
# when handling a relative filename.
if os.path.isabs(filename):
return []
for dirname in sys.path:
try:
fullname = os.path.join(dirname, basename)
except (TypeError, AttributeError):
# Not sufficiently string-like to do anything useful with.
continue
try:
stat = os.stat(fullname)
break
except OSError:
pass
else:
return []
try:
with tokenize.open(fullname) as fp:
lines = fp.readlines()
except OSError:
return []
if lines and not lines[-1].endswith('\n'):
lines[-1] += '\n'
size, mtime = stat.st_size, stat.st_mtime
cache[filename] = size, mtime, lines, fullname
return lines
def lazycache(filename, module_globals):
"""Seed the cache for filename with module_globals.
The module loader will be asked for the source only when getlines is
called, not immediately.
If there is an entry in the cache already, it is not altered.
:return: True if a lazy load is registered in the cache,
otherwise False. To register such a load a module loader with a
get_source method must be found, the filename must be a cachable
filename, and the filename must not be already cached.
"""
if filename in cache:
if len(cache[filename]) == 1:
return True
else:
return False
if not filename or (filename.startswith('<') and filename.endswith('>')):
return False
# Try for a __loader__, if available
if module_globals and '__loader__' in module_globals:
name = module_globals.get('__name__')
loader = module_globals['__loader__']
get_source = getattr(loader, 'get_source', None)
if name and get_source:
get_lines = functools.partial(get_source, name)
cache[filename] = (get_lines,)
return True
return False
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