pyrcf.utils.time_utils

Utilities for timer and rate-related functionalities.

Classes

`ClockBase`	Base class for any Clock implementation for pyrcf control loop and components.
`PythonEpochClock`	ClockBase implementation to query system time using time.time().
`PythonPerfClock`	ClockBase implementation to query counter using time.perf_counter(). Only
`RateLimiter`	Modified from https://github.com/upkie/loop-rate-limiters/blob/main/loop_rate_limiters/rate_limiter.py.
`RateTrigger`	Can be used to execute something at a specific rate. Checking

Module Contents

class pyrcf.utils.time_utils.ClockBase

Bases: abc.ABC

Base class for any Clock implementation for pyrcf control loop and components.

abstract get_time() → float

Get the latest time from this clock.

Raises:: NotImplementedError – Raised if this method is not implemented by the child class.
Returns:: the current time in seconds.
Return type:: float

class pyrcf.utils.time_utils.PythonEpochClock

Bases: ClockBase

ClockBase implementation to query system time using time.time().

get_time() → float

Get the latest time from this clock.

Raises:: NotImplementedError – Raised if this method is not implemented by the child class.
Returns:: the current time in seconds.
Return type:: float

class pyrcf.utils.time_utils.PythonPerfClock

Bases: ClockBase

ClockBase implementation to query counter using time.perf_counter(). Only meaningful when comparing values from other time.perf_counter() calls.

get_time() → float

Get the latest time from this clock.

Raises:: NotImplementedError – Raised if this method is not implemented by the child class.
Returns:: the current time in seconds.
Return type:: float

class pyrcf.utils.time_utils.RateLimiter(frequency: float, name: str = 'rate limiter', warn: bool = False, clock: ClockBase = PythonPerfClock())

Modified from https://github.com/upkie/loop-rate-limiters/blob/main/loop_rate_limiters/rate_limiter.py.

Original License terms below:

Regulate the frequency between calls to the same instruction.

This rate limniter is meant to be used in e.g. a loop or callback function. It is, in essence, the same as rospy.Rate. It assumes Python’s performance counter never jumps backward nor forward, so that it does not handle such cases contrary to rospy.Rate.

name: Human-readable name used for logging.

warn: If set (default), warn when the time between two calls exceeded the rate clock.

# # Copyright 2022 Stéphane Caron # Copyright 2023 Inria # # Licensed under the Apache License, Version 2.0 (the “License”); # you may not use this file except in compliance with the License. # You may obtain a copy of the License at # # http://www.apache.org/licenses/LICENSE-2.0 # # Unless required by applicable law or agreed to in writing, software # distributed under the License is distributed on an “AS IS” BASIS, # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. # See the License for the specific language governing permissions and # limitations under the License.

__period: float

__slack: float

__next_tick: float

__freq: float

name: str

warn: bool

set_frequency(frequency: float)

change_clock(clock: ClockBase)

property clock: ClockBase

The clock used by this class.

Use get_time() on this attribute to get current time in seconds.

Returns:: The clock object used by this class.
Return type:: ClockBase

property dt: float: Desired period between two calls to sleep(), in seconds.

property next_tick: float: Time of next clock tick.

property period: float: Desired period between two calls to sleep(), in seconds.

property frequency: float: Desired frequency between two calls to sleep(), in seconds.

property slack: float

Slack duration computed at the last call to sleep().

This duration is in seconds.

remaining() → float

Get the time remaining until the next expected clock tick.

Returns:: Time remaining, in seconds, until the next expected clock tick.

sleep(): Sleep for the duration required to regulate inter-call frequency.

class pyrcf.utils.time_utils.RateTrigger(rate: float, clock: ClockBase = PythonPerfClock())

Can be used to execute something at a specific rate. Checking the .triggered() method of this class will return True or False depending on whether the specified rate has reached.

NOTE: Warning: When using this with RateLimiter in the same loop, try to keep the rate of this class a factor of the rate of the RateLimiter object. Otherwise, the RateTrigger will not be able to keep the required rate (because RateLimiter enforces a sleep). Make sure to use same clock as well.

__period

__next_tick = None

change_clock(clock: ClockBase)

property clock: ClockBase

The clock used by this class.

Use get_time() on this attribute to get current time in seconds.

Returns:: The clock object used by this class.
Return type:: ClockBase

property dt: float: Desired period between two calls to sleep(), in seconds.

property next_tick: float: Time of next clock tick.

property period: float: Desired period between two calls to sleep(), in seconds.

triggered() → bool: Check if the specified rate has been triggered.

property has_triggered: bool: Attribute to check if the specified rate has been triggered.

__call__() → bool: Calling this class object directly will check if the specified rate has been triggered.