music21.common.classTools

Functions

music21.common.classTools.classToClassStr(classObj: Type) → str

Convert a class object to a class string.

>>> common.classToClassStr(note.Note)
'Note'
>>> common.classToClassStr(chord.Chord)
'Chord'

music21.common.classTools.getClassSet(instance, classNameTuple=None)

Return the classSet for an instance (whether a Music21Object or something else). See base.Music21Object.classSet for more details.

>>> p = pitch.Pitch()
>>> cs = common.classTools.getClassSet(p)
>>> cs
 frozenset(...)
>>> pitch.Pitch in cs
True
>>> 'music21.pitch.Pitch' in cs
True
>>> 'Pitch' in cs
True
>>> object in cs
True
>>> 'object' in cs
True

To save time (this IS a performance-critical operation), classNameTuple can be passed a tuple of names such as (‘Pitch’, ‘object’) that will save the creation time of this set.

>>> cs2 = common.classTools.getClassSet(p, classNameTuple=('Pitch', 'ProtoM21Object'))
>>> 'Pitch' in cs2
True

Use base.Music21Object.classSet in general for music21Objects since it not only caches the result for each object, it caches the result for the whole class the first time it is run.

music21.common.classTools.isIterable(usrData: Any) → bool

Returns True if is the object can be iter’d over and is NOT a string

>>> common.isIterable([5, 10])
True
>>> common.isIterable('sharp')
False
>>> common.isIterable((None, None))
True
>>> common.isIterable(stream.Stream())
True

Ranges are not iterators by python 3, but return True

>>> common.isIterable(range(20))
True

Classes are not iterable even if their instances are:

>>> common.isIterable(stream.Stream)
False

Changed in v7.3 – Classes (not instances) are not iterable

music21.common.classTools.isListLike(usrData: Any) → bool

Returns True if is a List or Tuple or their subclasses.

Formerly allowed for set here, but that does not allow for subscripting (set([1, 2, 3])[0] is undefined).

Differs from isinstance(collections.abc.Sequence()) in that we do not want Streams included even if __contains__, __reversed__, and count are added, and we do not want to include str or bytes.

>>> common.isListLike([])
True
>>> common.isListLike('sharp')
False
>>> common.isListLike((None, None))
True
>>> common.isListLike({'a', 'b', 'c', 'c'})
False
>>> common.isListLike(stream.Stream())
False

music21.common.classTools.isNum(usrData: Any) → bool

check if usrData is a number (float, int, long, Decimal), return boolean

unlike isinstance(usrData, Number) does not return True for True, False.

Does not use isinstance(usrData, Number) which is 2-6 times slower than calling this function (except in the case of Fraction, when it’s 6 times faster, but that’s rarer). (6 times slower on Py3.4, now only 2x slower in Python 3.10)

Runs by adding 0 to the “number” – so anything that implements add to a scalar works

>>> common.isNum(3.0)
True
>>> common.isNum(3)
True
>>> common.isNum('three')
False
>>> common.isNum([2, 3, 4])
False

True and False are NOT numbers:

>>> common.isNum(True)
False
>>> common.isNum(False)
False
>>> common.isNum(None)
False

music21.common.classTools.saveAttributes(obj, *attributeList)

Save a number of attributes in an object and then restore them afterwards.

>>> p = pitch.Pitch('C#2')
>>> with common.classTools.saveAttributes(p, 'name', 'accidental'):
...     p.step = 'E'
...     p.accidental = pitch.Accidental('flat')
...     p.nameWithOctave
'E-2'
>>> p.nameWithOctave
'C#2'

For storing and setting a value on a single attribute see tempAttribute().

New in v7.

music21.common.classTools.tempAttribute(obj, attribute: str, new_val=<object object>)

Temporarily set an attribute in an object to another value and then restore it afterwards.

>>> p = pitch.Pitch('C4')
>>> p.midi
60
>>> with common.classTools.tempAttribute(p, 'nameWithOctave', 'D#5'):
...     p.midi
75
>>> p.nameWithOctave
'C4'

Setting to a new value is optional.

For working with multiple attributes see saveAttributes().

New in v7.