DADAHeader

class baseband.dada.header.DADAHeader(*args, verify=True, mutable=True, **kwargs)

Bases: OrderedDict

DADA baseband file format header.

Defines a number of routines common to all baseband format headers.

Parameters:

*argsstr or iterable

If a string, parsed as a DADA header from a file, otherwise as for the OrderedDict baseclass.

verifybool, optional

Whether to do minimal verification that the header is consistent with the DADA standard. Default: True.

mutablebool, optional

Whether to allow the header to be changed after initialisation. Default: True.

**kwargs

Any further header keywords to be set. If any value is a 2-item tuple, the second one will be considered a comment.

Notes

Like OrderedDict, in order to ensure keywords are kept in the right order, one should pass on values as a tuple, not as a dict. E.g., to copy a header, one should not do DADAHeader(**header), but rather:

DADAHeader(((key, header[key]) for key in header))

or, to also keep the comments:

DADAHeader(((key, (header[key], header.comments[key]))
           for key in header))

Attributes Summary

bps	Bits per elementary sample.
complex_data	Whether the data are complex.
frame_nbytes	Size of the frame in bytes.
nbytes	Size of the header in bytes.
offset	Offset from start of observation in units of time.
payload_nbytes	Size of the payload in bytes.
sample_rate	Number of complete samples per second.
sample_shape	Shape of a sample in the payload (npol, nchan).
samples_per_frame	Number of complete samples in the frame.
sideband	True if upper sideband.
start_time	Start time of the observation.
time	Start time of the part of the observation covered by this header.

Methods Summary

clear()
copy()	Create a mutable and independent copy of the header.
fromfile(fh[, verify])	Reads in DADA header block from a file.
fromkeys(*args, **kwargs)	Initialise a header from keyword values.
fromvalues(**kwargs)	Initialise a header from parsed values.
get(key[, default])	Return the value for key if key is in the dictionary, else default.
items()
keys()
move_to_end(/, key[, last])	Move an existing element to the end (or beginning if last is false).
pop(/, key[, default])	If the key is not found, return the default if given; otherwise, raise a KeyError.
popitem(/[, last])	Remove and return a (key, value) pair from the dictionary.
setdefault(/, key[, default])	Insert key with a value of default if key is not in the dictionary.
tofile(fh)	Write DADA file header to filehandle.
update(*[, verify])	Update the header with new values.
values()
verify()	Basic check of integrity.

Attributes Documentation

bps

Bits per elementary sample.

complex_data

Whether the data are complex.

frame_nbytes

Size of the frame in bytes.

nbytes

Size of the header in bytes.

offset

Offset from start of observation in units of time.

payload_nbytes

Size of the payload in bytes.

sample_rate

Number of complete samples per second.

Can be set with a negative quantity to set sideband.

sample_shape

Shape of a sample in the payload (npol, nchan).

samples_per_frame

Number of complete samples in the frame.

sideband

True if upper sideband.

start_time

Start time of the observation.

time

Start time of the part of the observation covered by this header.

Methods Documentation

clear() → None.  Remove all items from od.

copy()

Create a mutable and independent copy of the header.

classmethod fromfile(fh, verify=True)

Reads in DADA header block from a file.

The file pointer should be at the start.

Parameters:

fhfilehandle

To read data from.

verify: bool, optional

Whether to do basic checks on whether the header is valid. Default: True.

classmethod fromkeys(*args, **kwargs)

Initialise a header from keyword values.

Like fromvalues, but without any interpretation of keywords.

This just calls the class initializer; it is present for compatibility with other header classes only.

classmethod fromvalues(**kwargs)

Initialise a header from parsed values.

Here, the parsed values must be given as keyword arguments, i.e., for any header, cls.fromvalues(**header) == header.

However, unlike for the fromkeys class method, data can also be set using arguments named after header methods, such as time.

Furthermore, some header defaults are set in DADAHeader._defaults.

get(key, default=None, /)

Return the value for key if key is in the dictionary, else default.

items() → a set-like object providing a view on D's items

keys() → a set-like object providing a view on D's keys

move_to_end(/, key, last=True)

Move an existing element to the end (or beginning if last is false).

Raise KeyError if the element does not exist.

pop(/, key, default=<unrepresentable>)

If the key is not found, return the default if given; otherwise, raise a KeyError.

popitem(/, last=True)

Remove and return a (key, value) pair from the dictionary.

Pairs are returned in LIFO order if last is true or FIFO order if false.

setdefault(/, key, default=None)

Insert key with a value of default if key is not in the dictionary.

Return the value for key if key is in the dictionary, else default.

tofile(fh)

Write DADA file header to filehandle.

Parts of the header beyond the ascii lines are filled with 0x00. Note that file should in principle be at the start, but we don’t check for that since that would break SequentialFileWriter.

update(*, verify=True, **kwargs)

Update the header with new values.

Here, any keywords matching properties are processed as well, in the order set by the class (in _properties), and after all other keywords have been processed.

Parameters:

verifybool, optional

If True (default), verify integrity after updating.

**kwargs

Arguments used to set keywords and properties.

values() → an object providing a view on D's values

verify()

Basic check of integrity.