Examples

Installation

This is only required on your first use.

• Ensure you have Pip, then install Pytac and Cothread:

  $ pip install pytac
  $ pip install cothread
  $ # Cothread is required for EPICS functionality, but Pytac can run without it.
  

Initialisation

This is required each time you want to start up Pytac.

• Navigate to your Pytac directory and start Python:

  $ cd <directory-path>
  $ python
  Python 2.7.3 (default, Nov  9 2013, 21:59:00)
  [GCC 4.4.7 20120313 (Red Hat 4.4.7-3)] on linux2
  Type "help", "copyright", "credits" or "license" for more information.
  >>>
  

• Import Pytac and initialise the lattice from the VMX directory:

  >>> import pytac.load_csv
  >>> lattice = pytac.load_csv.load('VMX')
  

The lattice object is used for interacting with elements of the accelerator.

Print BPM PV names along with s position

• Get all elements that represent BPM s:

  >>> bpms = lattice.get_elements('BPM')
  

• Print the device names and s position of each BPM:

  >>> for bpm in bpms:
  >>>    print('BPM {} at position {}'.format(bpm.get_device('x').name, bpm.s))
  BPM SR01C-DI-EBPM-01 at position 4.38
  BPM SR01C-DI-EBPM-02 at position 8.8065
  BPM SR01C-DI-EBPM-03 at position 11.374
  BPM SR01C-DI-EBPM-04 at position 12.559
  BPM SR01C-DI-EBPM-05 at position 14.9425
  ...
  

• Get PV names and positions for BPMs directly from the lattice object:

  >>> lattice.get_element_pv_names('BPM', 'x', pytac.RB)
  ['SR01C-DI-EBPM-01:SA:X',
  'SR01C-DI-EBPM-02:SA:X',
  'SR01C-DI-EBPM-03:SA:X'
  ...
  >>> lattice.get_element_pv_names('BPM', 'y', pytac.RB)
  ['SR01C-DI-EBPM-01:SA:Y',
  'SR01C-DI-EBPM-02:SA:Y',
  'SR01C-DI-EBPM-03:SA:Y',
  ...
  >>> lattice.get_family_s('BPM')
  [4.38,
  8.806500000000002,
  11.374000000000002,
  ...
  

Get the value of the ‘b1’ field of the quad elements

• Get all Quadrupole elements and print their ‘b1’ field read back values:

  >>> quads = lattice.get_elements('QUAD')
  >>> for quad in quads:
  >>>    print(quad.get_value('b1', pytac.RB))
  71.3240509033
  129.351394653
  98.2537231445
  ...
  

• Print the QUAD read back values of the ‘b1’ field using the lattice. This is more efficient since it uses only one request to the control system:

  >>> lattice.get_values('QUAD', 'b1', pytac.RB)
  [71.32496643066406,
  129.35191345214844,
  98.25287628173828,
  ...
  

Tutorial

For an introduction to pytac concepts and finding your way around, an interactive tutorial is available using Jupyter Notebook. Take a look in the jupyter directory - the README.rst there describes how to access the tutorial.