the-collector 0.8.6

A library to store robot data in common formats

The Collector

This is still under heavy development

The idea behind this a container that can store data and time tag the data when it is captured. The main structure is a dict which has keys for each data series stored.

This was written for a class I taught on robotics. It is meant to be simple and teach the students some things. There are probably better solutions out there, but I like this.

Additionally, there is nothing magically about what this does:

• It provides a generic interface to using pickle or json as the protocol for saving data to disk
• It also allows you to convert between them if needed
• Bag files can be read using the original protocol, thus data is never lost if this library goes away
• Designed to be simple and straight forward

Setup

Install

The suggested way to install this is via the pip command as follows:

pip install the_collector
pip install the_collector[numpy]

If you install numpy, then you get access to working with numpy arrays using the functions: array_pack() and array_pack(). These really don't save you much.

Usage

BagIt

Bag stores data in memory until the buffer size limit is reached then it dumps the data to a file.

#!/usr/bin/env python3
from __future__ import print_function
from the_collector import BagIt
from the_collector import Json, Pickle
import json


d = {'a': 1, 'b': 2}

bag = BagIt(Json)      # ascii, cross platform
# bag = BagIt(Pickle)  # binary, python only but handles python objects well

for i in range(10):
    bag.push('test', d) # push value d to key 'test'
    bag.push('bob', d)
    bag.push('tom', ('a', i,))

# timestamp adds a timestamp automatically to the bag file. Thus, you won't
# over write bob.json.bag each time you run this program because the filename
# is bob-2019-04-20-15:35:25.6543.json.bag
fname = bag.write('bob', timestamp=False)

print(">> created:", fname)

data = bag.read(fname) # data is just a dictionary
print(data)

Now, since there is nothing super special the_collector does with packing data, you can always read the bag files using the original libraries:

with open(fname, 'rb') as fd:
    data = json.load(fd)

for key, val in data.items():
    print("{}[{}]".format(key, len(val)))
    for v in val:
        print("{}".format(v), end=' ')
        print(' ')

Circular Buffer

This is perhaps a little out of place, but I use circular buffers with handling data so I stuck it in this library.

from the_collector import CircularBuffer

cb = CircularBuffer(60)  # can only hold 60 items before it copies over data

# Let's push way more than 60 things
for i in range(200):
    cb.push(i)

print(cb.get_all())  # print everything
print('get cb[7]', cb[7])
print('get cb[0]', cb[0])
print('get last', cb.get_last())

Data Tuple

Use a generic namedtuple for data storage. It will automatically insert a timestamp when created. This is useful for tagging data with a timestamp and not having to remember to do it yourself.

WARNING: json and msgpack have issues with tuples, so this is best used with pickle or you have to accept json will turn it into a list and msgpack will turn it into a regular tuple. Either way, you still keep the timestamp.

from the_collector import Data

d = Data((1,2,3,))  # timestamp generate when made

print("Data[{}]: {}".format(d.timestamp, d.data))
print("Namedtuple output:", d)

Todo

• add github actions
• look at enabling BytesIO for testing/working so you don't litter filing system with test bag files
• support PEP517 and replace setup.py with pyprogram.toml
• move tests from nose to pytest
• remove msgpack, there is no advantage to it over pickle(python only) or json(cross platform)
• add json compression back in

Change Log

Date	Version	Notes
2020-04-19	0.8.5	removed msgpack
2019-07-06	0.8.2	add generic data container
2019-04-28	0.8.0	can store data using json, pickle, or msgpack
2018-07-25	0.7.0	added msgpack messages and a way to do custom messages
2018-07-14	0.6.0	changed interface to support buffered writing to disk
2018-07-09	0.5.0	moved away from json and now using msgpack
2017-11-23	0.4.0	fixes, documentation, unit tests
2017-10-04	0.0.1	init

The MIT License (MIT)

Copyright (c) 2017 Kevin J. Walchko

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.