prevo 0.9.0

Record arbitrary sensors periodically in an asynchronous manner. Control their properties in real time from CLI. Graph/view tools to visualize live data/images are also provided.

About

Periodic REcording and Visualization of (sensor) Objects

This package provides base classes to rapidly create interactive data recording for various applications (e.g. recording of temperature, time-lapses with cameras etc.). Sensors are read in a asynchronous fashion and can have different time intervals for data reading (or be continuous, i.e. as fast as possible). Tools for graphical visualizations of data during recording are also provided.

Install

pip install prevo

Main Contents

For using the package for asynchronous recording of data, three base classes must/can be subclassed:

• SensorBase (requires subclassing)
• RecordingBase (requires subclassing)
• RecordBase (can be used as is or be subclassed)

A minimal example is provided below, to record pressure and temperature asynchronously, assuming the user already has classes (Temp, Gauge) to take single-point measurements (it could be functions as well). Let's assume that the pressure measurement also has an averaging parameter to smooth the data.

1. Define the sensors

   from prevo.record import SensorBase
   
   
   class TemperatureSensor(SensorBase):
   
       name = 'T'
   
       def _read(self):
           """This method must have no arguments"""
           return Temp.read()
   
   
   class PressureSensor(SensorBase):
   
       name = 'P'
   
       def __init__(self):
           self.avg = 10  # default value
   
       def _read(self):
           return Gauge.read(averaging=self.avg)
   

2. Define the individual recordings

   Note: subclassing can help significantly reduce the code below.

   from prevo.record import RecordingBase
   
   
   class RecordingT(RecordingBase):
       """Recording temperature data periodically"""
   
       def __init__(self):
   
           super().__init__(Sensor=TemperatureSensor,
                            dt=10)  # by default, record every 10 sec
           self.file = 'Temperature.txt'
           # Below, this allows the user to change time interval in real time
           self.controlled_properties = 'timer.interval',
   
       def init_file(self, file):
           """Define if you want to write column titles etc.
           (assuming the file is already open)
           """
           pass
   
       def format_measurement(self, data):
           """Define here how to format data from Sensor._read().
           (e.g., add time information, etc.). Returns a 'measurement'."""
           pass
   
       def save(self, measurement, file):
           """Define here how to save the measurement above into self.file.
           (assuming the file is already open)
           """
           pass
   
   
   class RecordingP(RecordingBase):
       """Recording pressure data periodically"""
   
       def __init__(self):
   
           super().__init__(Sensor=PressureSensor,
                            dt=1)  # by default, record every second
           self.file = 'Pressure.txt'
           # Here we can also control the averaging in real time
           self.controlled_properties = 'timer.interval', 'sensor.avg'
   
       def init_file(self, file):
           """same as above"""
           pass
   
       def format_measurement(self, data):
           """same as above"""
           pass
   
       def save(self):
           """same as above"""
           pass
   

3. Define and start asynchronous recording

   from prevo.record import RecordBase
   
   
   class Record(RecordBase):
       """Options exist to add metadata saving or graphing"""
       pass
   
   
   # Keys must correspond to sensor names
   recordings = {'T': RecordingT(), 'P': RecordingP()}
   
   # All properties that can be controlled by CLI
   # (keys must correspond to some controlled_properties)
   properties = {'timer.interval': {'repr': 'Δt (s)',
                                    'commands': ('dt',),
                                    },
                 'sensor.avg': {'repr': 'Averaging',
                                'commands': ('avg',),
                                }
                 }
   
   # Start recording. A CLI will appear; type '?' for help
   Record(recordings=recordings, properties=properties).start()
   

Note: context managers also possible (i.e. define __enter__ and __exit__ in Sensor class) e.g. if sensors have to be opened once at the beginning and closed in the end; this is managed automatically by RecordBase if a context manager is defined.

See docstrings for more help.

Additional tools

Some elements are also provided to simplify and/or extend the classes above:

• plot numerical data in real time (see prevo.plot module and GraphExamples.ipynb)
• live view images from camera-like sensors (see prevo.viewers)
• read / save with CSV files (see prevo.csv)
• parse command line arguments to trigger functions or class methods (see prevo.parser)
• some tools to format measurements for Record-like classes (see prevo.measurements)

See docstrings for more help.

Misc. info

Module requirements

Packages outside of standard library

(installed automatically by pip if necessary)

• tqdm
• tzlocal < 3.0
• oclock >= 1.2.2 (timing tools)
• clivo >= 0.2.0 (command line interface)
• matplotlib >= 3.1 (due to cache_frame_data option in FuncAnimation)
• numpy

Optional packages

• pandas (optional, for csv loading methods)
• opencv-python (optional, for specific camera viewers)

Python requirements

Python : >= 3.6

Author

Olivier Vincent

([e-mail])