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 3.7.2 (default, Jan 20 2020, 11:03:41)
[GCC 4.8.5 20150623 (Red Hat 4.8.5-39)] on linux
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('Quadrupole')
>>> for quad in quads:
>>>    print(quad.get_value('b1', pytac.RB))
71.3240509033
129.351394653
98.2537231445
...

Print the Quadrupole 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_element_values('Quadrupole', '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.