GUPPIFrame

class baseband.guppi.GUPPIFrame(header, payload, valid=True, verify=True)

Bases: baseband.vlbi_base.frame.VLBIFrameBase

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

Parameters:

header : GUPPIHeader

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

payload : GUPPIPayload

Wrapper around the payload, provding mechanisms to decode it.

valid : bool, optional

Whether the data are valid. Default: True.

verify : bool, optional

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

Notes

GUPPI 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 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, possible mapping the payload.
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=True, verify=True, **kwargs)

Construct frame from data and header.

Note that since GUPPI files are generally very large, one would normally map the file, and then set pieces of it by assigning to slices of the frame. See memmap_frame.

Parameters:

data : ndarray

Array holding complex or real data to be encoded.

header : GUPPIHeader or None, optional

If not given, will attempt to generate one using the keywords.

valid : bool, optional

Whether the data are valid (default: True). Note that this information cannot be written to disk.

verify : bool, optional

Whether or not to do basic assertions that check the integrity. Default: True.

**kwargs

If header is not given, these are used to initialize one.

classmethod fromfile(fh, memmap=True, valid=True, verify=True)

Read a frame from a filehandle, possible mapping the payload.

Parameters:

fh : filehandle

To read header from.

memmap : bool, optional

If True (default), use memmap to map the payload. If False, just read it from disk.

valid : bool, optional

Whether the data are valid (default: True). Note that this cannot be inferred from the header or payload itself. If False, any data read will be set to cls.fill_value.

verify : bool, optional

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

keys()

tofile(fh)

Write encoded frame to filehandle.

verify()

Simple verification. To be added to by subclasses.