rdrecord(smooth_frames=False) fails if max(spf) == 1

[bemoody]

If rdrecord is invoked with:

• smooth_frames=True and physical=True (default), it should set rec.p_signal to a two-dimensional floating-point array.
• smooth_frames=True and physical=False, it should set rec.d_signal to a two-dimensional integer array.
• smooth_frames=False and physical=True, it should set rec.e_p_signal to a list of floating-point arrays.
• smooth_frames=False and physical=False, it should set rec.e_d_signal to a list of integer arrays.

For example:

>>> type(wfdb.rdrecord('sample-data/03700181', smooth_frames=True, physical=True).p_signal)
<class 'numpy.ndarray'>
>>> type(wfdb.rdrecord('sample-data/03700181', smooth_frames=True, physical=False).d_signal)
<class 'numpy.ndarray'>
>>> type(wfdb.rdrecord('sample-data/03700181', smooth_frames=False, physical=True).e_p_signal)
<class 'list'>
>>> type(wfdb.rdrecord('sample-data/03700181', smooth_frames=False, physical=False).e_d_signal)
<class 'list'>

However, if every signal in the record has exactly one sample per frame, this doesn't work:

>>> type(wfdb.rdrecord('sample-data/100', smooth_frames=True, physical=True).p_signal)
<class 'numpy.ndarray'>
>>> type(wfdb.rdrecord('sample-data/100', smooth_frames=True, physical=False).d_signal)
<class 'numpy.ndarray'>
>>> type(wfdb.rdrecord('sample-data/100', smooth_frames=False, physical=True).e_p_signal)
<class 'NoneType'>
>>> type(wfdb.rdrecord('sample-data/100', smooth_frames=False, physical=False).e_d_signal)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/benjamin/wfdb-python/wfdb/io/record.py", line 3637, in rdrecord
    record.convert_dtype(physical, return_res, smooth_frames)
  File "/home/benjamin/wfdb-python/wfdb/io/_signal.py", line 726, in convert_dtype
    current_dtype = self.e_d_signal[ch].dtype
TypeError: 'NoneType' object is not subscriptable

[bemoody]

Of course it gets even thornier if the record has multiple spf but you select signal(s) that have only one spf:

>>> wfdb.rdrecord('sample-data/03700181', smooth_frames=False, channels=[1])
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/benjamin/wfdb-python/wfdb/io/record.py", line 3536, in rdrecord
    expanded=False)
  File "/home/benjamin/wfdb-python/wfdb/io/record.py", line 706, in _arrange_fields
    if self.sig_len != self.d_signal.shape[0]:
AttributeError: 'list' object has no attribute 'shape'

(because then _rd_dat_signals and _rd_segment return a list of arrays but rdrecord is expecting a 2D array.)