DADAHeader

class baseband.dada.DADAHeader(*args, **kwargs)

Bases: collections.OrderedDict

DADA baseband file format header.

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

Parameters:

*args : str or iterable

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

verify : bool, optional

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

mutable : bool, 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(k[,d])
has_key(k)
items()
iteritems()	od.iteritems -> an iterator over the (key, value) pairs in od
iterkeys()
itervalues()	od.itervalues -> an iterator over the values in od
keys()
pop(k[,d])	value.
popitem()	Pairs are returned in LIFO order if last is true or FIFO order if false.
setdefault(k[,d])
tofile(fh)	Write DADA file header to filehandle.
update(**kwargs)	Update the header with new values.
values()
verify()	Basic check of integrity.
viewitems()
viewkeys()
viewvalues()

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:

fh : filehandle

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(k[, d]) → D[k] if k in D, else d. d defaults to None.

has_key(k) → True if D has a key k, else False

items() → list of (key, value) pairs in od

iteritems()

od.iteritems -> an iterator over the (key, value) pairs in od

iterkeys() → an iterator over the keys in od

itervalues()

od.itervalues -> an iterator over the values in od

keys() → list of keys in od

pop(k[, d]) → v, remove specified key and return the corresponding

value. If key is not found, d is returned if given, otherwise KeyError is raised.

popitem() → (k, v), return and remove a (key, value) pair.

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

setdefault(k[, d]) → od.get(k,d), also set od[k]=d if k not in od

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(**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:

verify : bool, optional

If True (default), verify integrity after updating.

**kwargs

Arguments used to set keywords and properties.

values() → list of values in od

verify()

Basic check of integrity.

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

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

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