pybricks.tools
wait
pybricks.tools.StopWatch
pybricks.tools.StopWatch.time
pybricks.tools.StopWatch.pause
pybricks.tools.StopWatch.resume
pybricks.tools.StopWatch.reset
pybricks.tools.DataLog
pybricks.tools.DataLog.log
By default, this class creates a csv file on the EV3 brick with the name log and the current date and time. For example, if you use this class on 13 February 2020 on 10:07 and 44.431260 seconds, the file is called log_2020_02_13_10_07_44_431260.csv.
See managing files on the EV3 <managefiles> to learn how to upload the log file back to your computer.
Example
This example shows how to log the angle of a rotating wheel as time passes.
../../pybricks-projects/snippets/ev3/datalog/main.py
In this example, the generated file has the following contents:
time, angle
3, 0
108, 6
212, 30
316, 71
419, 124
523, 176
628, 228
734, 281
838, 333
942, 385When you upload the file to your computer as shown above, you can open it in a spreadsheet editor. You can then generate a graph of the data, as shown in fig_datalog_graph.
In this example, we see that the motor angle changes slowly at first. Then the angle begins to change faster, and the graph becomes a straight line. This means that the motor has reached a constant speed. You can verify that the angle increases by 500 degrees per second.
Original file contents (left) and a generated graph (right).
Example
This example shows how to log data beyond just numbers. It also shows how you can use the optional arguments of the DataLog class to choose the file name and extension.
In this example, timestamp=False, which means that the date and time are not added to the file name. This can be convenient because the file name will always be the same. However, this means that the contents of my_file.txt will be overwritten every time you run this script.
../../pybricks-projects/snippets/ev3/datalog_extra/main.py