On 23.06.2015 01:15, Paul Sokolovsky wrote:
Hello from MicroPython, a lean Python implementation scaling down to run even on microcontrollers (https://github.com/micropython/micropython).
Our target hardware base oftentimes lacks floating point support, and using software emulation is expensive. So, we would like to have versions of some timing functions, taking/returning millisecond and/or microsecond values as integers.
The most functionality we're interested in:
1. Delays 2. Relative time (from an arbitrary starting point, expected to be wrapped) 3. Calculating time differences, with immunity to wrap-around.
The first presented assumption is to use "time.sleep()" for delays, "time.monotonic()" for relative time as the base. Would somebody gave alternative/better suggestions?
Second question is how to modify their names for millisecond/microsecond versions. For sleep(), "msleep" and "usleep" would be concise possibilities, but that doesn't map well to monotonic(), leading to "mmonotonic". So, better idea is to use "_ms" and "_us" suffixes:
sleep_ms() sleep_us() monotonic_ms() monotonic_us()
Point 3 above isn't currently addressed by time module at all. https://www.python.org/dev/peps/pep-0418/ mentions some internal workaround for overflows/wrap-arounds on some systems. Due to lean-ness of our hardware base, we'd like to make this matter explicit to the applications and avoid internal workarounds. Proposed solution is to have time.elapsed(time1, time2) function, which can take values as returned by monotonic_ms(), monotonic_us(). Assuming that results of both functions are encoded and wrap consistently (this is reasonable assumption), there's no need for 2 separate elapsed_ms(), elapsed_us() function.
So, the above are rough ideas we (well, I) have. We'd like to get wider Python community feedback on them, see if there're better/alternative ideas, how Pythonic it is, etc. To clarify, this should not be construed as proposal to add the above functions to CPython.
You may want to use a similar approach as I have used in mxDateTime to express date/time values: http://www.egenix.com/products/python/mxBase/mxDateTime/ It uses an integer to represent days and a float to represent seconds since midnight (i.e. time of day). The concept has worked out really well and often makes date/time calculations a lot easier than trying to stuff everything into a single number and then having to deal things like leap seconds and rounding errors. In your case you'd use integers for both and nanoseconds as basis for the time of day integer. -- Marc-Andre Lemburg eGenix.com Professional Python Services directly from the Source (#1, Jun 24 2015)
Python Projects, Coaching and Consulting ... http://www.egenix.com/ mxODBC Plone/Zope Database Adapter ... http://zope.egenix.com/ mxODBC, mxDateTime, mxTextTools ... http://python.egenix.com/
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