1. asyncio
PyUGAT
February 23rd, 2014

2. What is asynchronous I/O?
●
Input and output operations: slooooow
–
●
●
Disks, network, SSD,
Blocking I/O: wait for I/O operation to complete
Non-blocking I/O: permits other processing to continue
before I/O operation has finished
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Non-blocking I/O == asynchronous I/O
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Platform-dependent low-level APIs
–
e.g. epoll (Linux), I/O Completion Ports (Windows, Solaris),
kqueue (BSD, Mac OS X), ...

3. Asynchronous I/O in Python
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asyncore and asynchat modules, select module
–
–
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inflexible API, too simplistic
select: only partial support on Windows
Existing frameworks:
–
Twisted (https://twistedmatrix.com/trac/)
–
Gevent (http://www.gevent.org/)
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Monkey-patching
–
Tornado (http://www.tornadoweb.org/)
–
Lack of compatibility

4. asyncio
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== Tulip
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Will be in standard library (Python 3.4)
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Python 3.3: pip install asyncio

5. yield from
(PEP 380)

6. for x in subgenerator:
yield x

7. _i = iter(EXPR)
try:
_y = next(_i)
except StopIteration as _e:
_r = _e.value
else:
while 1:
try:
_s = yield _y
except GeneratorExit as _e:
try:
_m = _i.close
except AttributeError:
pass
else:
_m()
raise _e
except BaseException as _e:
_x = sys.exc_info()
try:
_m = _i.throw
except AttributeError:
raise _e
else:
try:
_y = _m(*_x)
except StopIteration as _e:
_r = _e.value
break
else:
try:
if _s is None:
_y = next(_i)
else:
_y = _i.send(_s)
except StopIteration as _e:
_r = _e.value
break
RESULT = _r

8. RESULT = yield from EXPR

9. asyncio
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Event loop
●
Tasks and coroutines
●
Transports and protocols

10. Code