DADAStreamReader¶
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class
baseband.dada.base.
DADAStreamReader
(fh_raw, squeeze=True, subset=(), verify=True)[source] [edit on github]¶ Bases:
baseband.dada.base.DADAStreamBase
,baseband.vlbi_base.base.VLBIStreamReaderBase
DADA format reader.
Allows access to DADA files as a continuous series of samples.
Parameters: fh_raw : filehandle
Filehandle of the raw DADA stream.
squeeze : bool, optional
If
True
(default), remove any dimensions of length unity from decoded data.subset : indexing object or tuple of objects, optional
Specific components of the complete sample to decode (after possibly squeezing). If a single indexing object is passed, it selects polarizations. With a tuple, the first selects polarizations and the second selects channels. If the tuple is empty (default), all components are read.
verify : bool, optional
Whether to do basic checks of frame integrity when reading. The first frame of the stream is always checked, so
verify
is effective only when reading sequences of files. Default:True
.Attributes Summary
bps
Bits per elementary sample. complex_data
Whether the data are complex. dtype
fill_value
Value to use for invalid or missing data. header0
First header of the file. info
Standardized information on stream readers. ndim
Number of dimensions of the (squeezed/subset) stream data. sample_rate
Number of complete samples per second. sample_shape
Shape of a complete sample (possibly subset or squeezed). samples_per_frame
Number of complete samples per frame. shape
Shape of the (squeezed/subset) stream data. size
Total number of component samples in the (squeezed/subset) stream data. squeeze
Whether data arrays have dimensions with length unity removed. start_time
Start time of the file. stop_time
Time at the end of the file, just after the last sample. subset
Specific components of the complete sample to decode. time
Time of the sample pointer’s current offset in file. verify
Whether to do consistency checks on frames being read. Methods Summary
close
()read
([count, out])Read a number of complete (or subset) samples. seek
(offset[, whence])Change the stream position. tell
([unit])Current offset in the file. Attributes Documentation
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bps
¶ Bits per elementary sample.
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complex_data
¶ Whether the data are complex.
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dtype
¶
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fill_value
¶ Value to use for invalid or missing data. Default: 0.
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header0
¶ First header of the file.
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info
¶ Standardized information on stream readers.
The
info
descriptor provides a few standard attributes, all of which can also be accessed directly on the stream filehandle. More detailed information on the underlying file is stored in its info, accessible viainfo.file_info
.Attributes
start_time ( Time
) Time of the first complete sample.stop_time ( Time
) Time of the complete sample just beyond the end of the file.sample_rate ( Quantity
) Complete samples per unit of time.shape (tuple) Equivalent shape of the whole file, i.e., combining the number of complete samples and the shape of those samples. bps (int) Number of bits used to encode each elementary sample. complex_data (bool) Whether the data are complex.
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ndim
¶ Number of dimensions of the (squeezed/subset) stream data.
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sample_rate
¶ Number of complete samples per second.
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sample_shape
¶ Shape of a complete sample (possibly subset or squeezed).
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samples_per_frame
¶ Number of complete samples per frame.
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shape
¶ Shape of the (squeezed/subset) stream data.
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size
¶ Total number of component samples in the (squeezed/subset) stream data.
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squeeze
¶ Whether data arrays have dimensions with length unity removed.
If
True
, data read out has such dimensions removed, and data passed in for writing has them inserted.
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start_time
¶ Start time of the file.
See also
time
for the time of the sample pointer’s current offset, and (if available)stop_time
for the time at the end of the file.
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stop_time
¶ Time at the end of the file, just after the last sample.
See also
start_time
for the start time of the file, andtime
for the time of the sample pointer’s current offset.
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subset
¶ Specific components of the complete sample to decode.
The order of dimensions is the same as for
sample_shape
. Set by the class initializer.
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time
¶ Time of the sample pointer’s current offset in file.
See also
start_time
for the start time, and (if available)stop_time
for the end time, of the file.
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verify
¶ Whether to do consistency checks on frames being read.
Methods Documentation
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close
() [edit on github]¶
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read
(count=None, out=None) [edit on github]¶ Read a number of complete (or subset) samples.
The range retrieved can span multiple frames.
Parameters: count : int or None, optional
Number of complete/subset samples to read. If
None
(default) or negative, the whole file is read. Ignored ifout
is given.out : None or array, optional
Array to store the data in. If given,
count
will be inferred from the first dimension; the other dimension should equalsample_shape
.Returns: out :
ndarray
of float or complexThe first dimension is sample-time, and the remainder given by
sample_shape
.
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seek
(offset, whence=0) [edit on github]¶ Change the stream position.
This works like a normal filehandle seek, but the offset is in samples (or a relative or absolute time).
Parameters: offset : int,
Quantity
, orTime
Offset to move to. Can be an (integer) number of samples, an offset in time units, or an absolute time.
whence : {0, 1, 2, ‘start’, ‘current’, or ‘end’}, optional
Like regular seek, the offset is taken to be from the start if
whence=0
(default), from the current position if 1, and from the end if 2. One can alternativey use ‘start’, ‘current’, or ‘end’ for 0, 1, or 2, respectively. Ignored ifoffset
is a time.
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tell
(unit=None) [edit on github]¶ Current offset in the file.
Parameters: unit :
Unit
or str, optionalTime unit the offset should be returned in. By default, no unit is used, i.e., an integer enumerating samples is returned. For the special string ‘time’, the absolute time is calculated.
Returns: offset : int,
Quantity
, orTime
Offset in current file (or time at current position).
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