Parameters

data_models.parameters Module

We use the standard kwargs mechanism for arguments. For example:

kernelname = get_parameter(kwargs, "kernel", "2d")
oversampling = get_parameter(kwargs, "oversampling", 8)
padding = get_parameter(kwargs, "padding", 2)

The kwargs may need to be passed down to called functions.

All functions possess an API which is always of the form:

def processing_function(idatastruct1, idatastruct2, ..., *kwargs):
   return odatastruct1, odatastruct2,... other

Processing parameters are passed via the standard Python kwargs approach.

Inside a function, the values are retrieved can be accessed directly from the kwargs dictionary, or if a default is needed a function can be used:

log = get_parameter(kwargs, 'log', None)
vis = get_parameter(kwargs, 'visibility', None)

Function parameters should obey a consistent naming convention:

Name	Meaning
vis	Name of Visibility
sc	Name of Skycomponent
gt	Name of GainTable
conf	Name of Configuration
im	Name of input image
qa	Name of quality assessment
log	Name of processing log

If a function argument has a better, more descriptive name e.g. normalised_gt, newphasecentre, use it.

Keyword=value pairs should have descriptive names. The names should be lower case with underscores to separate words:

Name	Meaning	Example
loop_gain	Clean loop gain	0.1
niter	Number of iterations	10000
eps	Fractional tolerance	1e-6
threshold	Absolute threshold	0.001
fractional_threshold	Threshold as fraction of e.g. peak	0.1
G_solution_interval	Solution interval for G term	100
phaseonly	Do phase-only solutions	True
phasecentre	Phase centre (usually as SkyCoord)	SkyCoord(“-1.0d”, “37.0d”, frame=’icrs’, equinox=’J2000’)
spectral_mode	Visibility processing mode	‘mfs’ or ‘channel’

Functions

arl_path(path)	Converts a path that might be relative to ARL root into an absolute path.
get_parameter(kwargs, key[, default])	Get a specified named value for this (calling) function