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55 lines
1.7 KiB
Markdown
55 lines
1.7 KiB
Markdown
---
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title: "select"
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aliases:
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- firmwareapi/micropython/select.html
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- firmwareapi/micropython/select.md
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- chapter/firmwareapi/micropython/select
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---
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This module provides functions to wait for events on streams (select streams which are ready for operations).
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## Pyboard specifics
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Polling is an efficient way of waiting for read/write activity on multiple objects. Current objects that support polling are: `pyb.UART`, `pyb.USB_VCP`.
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## Methods
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#### select.poll()
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Create an instance of the `Poll` class.
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#### select.select(rlist, wlist, xlist\[, timeout\])
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Wait for activity on a set of objects.
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This function is provided for compatibility and is not efficient. Usage of `Poll` is recommended instead.
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## class Poll
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### Methods
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#### poll.register(obj\[, eventmask\])
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Register `obj` for polling. `eventmask` is logical OR of:
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* `select.POLLIN` - data available for reading
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* `select.POLLOUT` - more data can be written
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* `select.POLLERR` - error occurred
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* `select.POLLHUP` - end of stream/connection termination detected
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`eventmask` defaults to `select.POLLIN | select.POLLOUT`.
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#### poll.unregister(obj)
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Unregister `obj` from polling.
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#### poll.modify(obj, eventmask)
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Modify the `eventmask` for `obj`.
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#### poll.poll(\[timeout\])
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Wait for at least one of the registered objects to become ready. Returns list of (`obj`, `event`, ...) tuples, `event` element specifies which events happened with a stream and is a combination of `select.POLL*` constants described above. There may be other elements in tuple, depending on a platform and version, so don't assume that its size is 2. In case of timeout, an empty list is returned.
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Timeout is in milliseconds.
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