Tutorial¶

Concert is primarily a user interface to control devices commonly found at a Synchrotron beamline. This guide will briefly show you how to use and extend it.

Running a session¶

In case you don’t have a beamline at hand, you can import our sample sessions with the import command:

$ concert import --repo https://github.com/ufo-kit/concert-examples

Now start the tutorial session:

$ concert start tutorial

You will be greeted by an IPython shell loaded with pre-defined devices, processes and utilities like the pint package for unit calculation. Although, this package is primarily used for talking to devices, you can also use it to do simple calculations:

tutorial > a = 9.81 * q.m / q.s**2
tutorial > "Velocity after 5 seconds: {0}".format(5 * q.s * a)

'Velocity after 5 seconds: 49.05 meter / second'

You can get an overview of all defined devices by calling the ddoc() function:

tutorial > ddoc()

------------------------------------------------------------------------------
  Name         Description   Parameters
------------------------------------------------------------------------------
  motor        None           Name      Access  Unit  Description
                              position  rw      m     Position of the motor
------------------------------------------------------------------------------
  ...

Now, by typing just the name of a device, you can see it’s currently set parameter values:

tutorial > motor

<concert.devices.motors.dummy.LinearMotor object at 0x9419f0c>
 Parameter  Value
 position   12.729455653 millimeter

To get an overview of all devices’ parameter values, use the dstate() function:

tutorial > dstate()

---------------------------------------------
  Name         Parameters
---------------------------------------------
  motor        position  99.382 millimeter
---------------------------------------------
  ...

To change the value of a parameter, you simply assign a new value to it:

tutorial > motor.position = 2 * q.mm

Now, check the position to verify that the motor reached the target position:

tutorial > motor.position
<Quantity(2.0, 'millimeter')>

Depending on the device, changing a parameter will block as long as the device has not yet reached the final target state. You can read more about asynchronous execution in the Device control chapter.

Note

A parameter value is always checked for the correct unit and soft limit condition. If you get an error, check twice that you are using a compatible unit (setting two seconds on a motor position is obviously not) and are within the allowed parameter range.

pdoc() displays information about currently defined functions and processes and may look like this:

tutorial > pdoc()
------------------------------------------------------------------------------
Name                   Description
------------------------------------------------------------------------------
save_exposure_scan     Run an exposure scan and save the result as a NeXus
                       compliant file. This requires that libnexus and NexPy
                       are installed.
------------------------------------------------------------------------------

In case you are interested in the implementation of a function, you can use code_of(). For example:

tutorial > code_of(code_of)
def code_of(func):
    """Show implementation of *func*."""
    source = inspect.getsource(func)

    try:
        ...

Note

Because we are actually running an IPython shell, you can _always_ tab-complete objects and attributes. For example, to change the motor position to 1 millimeter, you could simply type mot<Tab>.p<Tab> = 1 * q.mm.

How to execute more things concurrently and how to stop execution can be found in Concurrent execution.

Creating a session¶

First of all, initialize a new session:

$ concert init new_session

and start the default editor with

$ concert edit new_session

At the top of the file, you can see a string enclosed in three ". This should be changed to something descriptive as it will be shown each time you start the session.

Sessions are just normal Python modules with one additional feature that you may use top-level await in them, i.e. outside of an async def function, for more info see Importing.

Adding devices¶

To create a device suited for your experiment you have to import it first. Concert uses the following packaging scheme to separate device classes and device implementations: concert.devices.[class].[implementation]. Thus if you want to create a dummy ring from the storage ring class, you would add this line to your session:

from concert.devices.storagerings.dummy import StorageRing

Once imported, you can create the device and give it a name that will be accessible from the command line shell:

from concert.devices.motors.dummy import LinearMotor

ring = await StorageRing()
motor = await LinearMotor()

Importing other sessions¶

To specify experiments that share a common set of devices, you can define a base session and import it from each sub-session:

from base import *

Now everything that was defined will be present when you start up the new session.

Hello World¶

Let’s create a session:

concert edit scan

And then add some code inside so that we can discuss some of the core Concert features. You can download the scan example or just copy this:

"""# *scan* shows scanning of camera's exposure time.

## Usage
    await run(producer, line, acc)

## Notes
"""

import asyncio
import logging
from inspect import iscoroutinefunction
import concert
concert.require("0.30.0")

from concert.coroutines.base import broadcast
from concert.coroutines.sinks import Accumulate
from concert.quantities import q
from concert.session.utils import cdoc, ddoc, dstate, pdoc, code_of
from concert.devices.cameras.dummy import Camera
from concert.ext.viewers import PyplotViewer, PyQtGraphViewer
from concert.processes.common import ascan

LOG = logging.getLogger(__name__)
# Disable progress bar in order not to interfere with printing
concert.config.PROGRESS_BAR = False


async def feedback():
    """Our feedback just returns image mean."""
    # Let's pretend this is a serious operation which takes a while
    await asyncio.sleep(1)
    image = await camera.grab()
    # Also show the current image
    await viewer.show(image)

    return image.mean()


async def run(producer, line, accumulator):
    coros = broadcast(producer, line, accumulator)
    await asyncio.gather(*coros)

    return accumulator.items


viewer = await PyQtGraphViewer()
# The last image will be quite bright
viewer.limits = 0, 10000
# Plot image mean
line = await PyplotViewer(style='-o')
# Dummy camera
camera = await Camera()
# For scan results collection
acc = Accumulate()
# Let's create a scan so that it can be directly plugged into *run*
producer = ascan(camera['exposure_time'], 1 * q.ms, 100 * q.ms, 10 * q.ms, feedback=feedback)

With this code you can execute the scan showing both the image and the mean and storing the result in acc by:

items = await run(producer, line, acc)
print(items) # or print(acc.items)
# Gives
[(1 <Unit('millisecond')>, 101.01860026041666),
 (11 <Unit('millisecond')>, 1101.0648697916668),
 (21 <Unit('millisecond')>, 2101.0111751302084),
 (31 <Unit('millisecond')>, 3100.9252408854168),
 (41 <Unit('millisecond')>, 4101.011533203125),
 (51 <Unit('millisecond')>, 5101.0090625),
 (61 <Unit('millisecond')>, 6100.966005859375),
 (71 <Unit('millisecond')>, 7101.112858072916),
 (81 <Unit('millisecond')>, 8100.928743489583),
 (91 <Unit('millisecond')>, 9101.179690755209)]

or you can simply run the scan showing both the image and the mean to see the mean:

await line(producer)

or you can iterate through the values and decide what to do with them yourself:

async for x, y in producer:
    print(f'x={x}, y={y}')
# Gives
x=1 millisecond, y=101.00574544270833
x=11 millisecond, y=1100.9828515625
x=21 millisecond, y=2100.9941015625
x=31 millisecond, y=3100.982431640625
x=41 millisecond, y=4100.772060546875
x=51 millisecond, y=5100.855152994792
x=61 millisecond, y=6100.988649088542
x=71 millisecond, y=7101.148798828125
x=81 millisecond, y=8101.085227864583
x=91 millisecond, y=9100.949088541667

Tutorial¶

Running a session¶

Creating a session¶

Adding devices¶

Importing other sessions¶

Hello World¶

Concert

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