DADAFrame

class baseband.dada.frame.DADAFrame(header, payload, valid=None, verify=True)

Bases: FrameBase

Representation of a DADA file, consisting of a header and payload.

Parameters:

headerDADAHeader

Wrapper around the header lines, providing access to the values.

payloadDADAPayload

Wrapper around the payload, provding mechanisms to decode it.

validbool, optional

Whether the data are valid. Default: True.

verifybool, optional

Whether to do basic verification of integrity. Default: True.

Notes

DADA files do not support storing whether data are valid or not on disk. Hence, this has to be determined independently. If valid=False, any decoded data are set to cls.fill_value (by default, 0).

The Frame can also be instantiated using class methods:

fromfile : read header and map or read payload from a filehandle

fromdata : encode data as payload

Of course, one can also do the opposite:

tofile : method to write header and payload to filehandle

data : property that yields full decoded payload

One can decode part of the payload by indexing or slicing the frame.

A number of properties are defined: shape, dtype and size are the shape, type and number of complete samples of the data array, and nbytes the frame size in bytes. Furthermore, the frame acts as a dictionary, with keys those of the header. Any attribute that is not defined on the frame itself, such as .time will be looked up on the header as well.

Attributes Summary

data	Full decoded frame.
dtype	Numeric type of the frame data.
fill_value	Value to replace invalid data in the frame.
nbytes	Size of the encoded frame in bytes.
ndim	Number of dimensions of the frame data.
sample_shape	Shape of a sample in the frame (nchan,).
shape	Shape of the frame data.
size	Total number of component samples in the frame data.
valid	Whether frame contains valid data.

Methods Summary

fromdata(data[, header, valid, verify])	Construct frame from data and header.
fromfile(fh[, memmap, valid, verify])	Read a frame from a filehandle.
keys()
tofile(fh)	Write encoded frame to filehandle.
verify()	Simple verification.

Attributes Documentation

data

Full decoded frame.

dtype

Numeric type of the frame data.

fill_value

Value to replace invalid data in the frame.

nbytes

Size of the encoded frame in bytes.

ndim

Number of dimensions of the frame data.

sample_shape

Shape of a sample in the frame (nchan,).

shape

Shape of the frame data.

size

Total number of component samples in the frame data.

valid

Whether frame contains valid data.

Methods Documentation

classmethod fromdata(data, header=None, *, valid=None, verify=True, **kwargs)

Construct frame from data and header.

Parameters:

datandarray

Array holding data to be encoded.

headerheader instance, optional

Header for the frame.

validbool, optional

Whether the data are valid. Default: inferred from header if possible, otherwise True.

verifybool, optional

Whether to verify the header and frame correctness.

**kwargs

Used to initialize the header, if not given.

classmethod fromfile(fh, memmap=None, valid=None, verify=True, **kwargs)

Read a frame from a filehandle.

Parameters:

fhfilehandle

Handle to read the frame from

memmapbool, optional

If False, read payload from file. If True, map the payload in memory (see memmap). Only useful for large payloads. Default: as set by payload class.

validbool, optional

Whether the data are valid. Default: inferred from header or payload read from file if possible, otherwise True.

verifybool, optional

Whether to do basic verification of integrity. Default: True.

**kwargs

Extra arguments that help to initialize the payload.

keys()

tofile(fh)

Write encoded frame to filehandle.

verify()

Simple verification. To be added to by subclasses.