Source code for pydicom.sequence

# Copyright 2008-2018 pydicom authors. See LICENSE file for details.
"""Define the Sequence class, which contains a sequence DataElement's items.

Sequence is a list of pydicom Dataset objects.

from pydicom.dataset import Dataset
from pydicom.multival import MultiValue

[docs]def validate_dataset(elem): """Check that `elem` is a Dataset instance.""" if not isinstance(elem, Dataset): raise TypeError('Sequence contents must be Dataset instances.') return elem
[docs]class Sequence(MultiValue): """Class to hold multiple Datasets in a list. This class is derived from MultiValue and as such enforces that all items added to the list are Dataset instances. In order to due this, a validator is substituted for type_constructor when constructing the MultiValue super class """ def __init__(self, iterable=None): """Initialize a list of Datasets. Parameters ---------- iterable : list-like of pydicom.dataset.Dataset, optional An iterable object (e.g. list, tuple) containing Datasets. If not used then an empty Sequence is generated. """ # We add this extra check to throw a relevant error. Without it, the # error will be simply that a Sequence must contain Datasets (since a # Dataset IS iterable). This error, however, doesn't inform the user # that the actual issue is that their Dataset needs to be INSIDE an # iterable object if isinstance(iterable, Dataset): raise TypeError('The Sequence constructor requires an iterable') # If no inputs are provided, we create an empty Sequence if not iterable: iterable = list() # validate_dataset is used as a pseudo type_constructor super(Sequence, self).__init__(validate_dataset, iterable) def __str__(self): """String description of the Sequence.""" lines = [str(x) for x in self] return "[" + "".join(lines) + "]" def __repr__(self): """String representation of the Sequence.""" formatstr = "<%(classname)s, length %(count)d>" return formatstr % { 'classname': self.__class__.__name__, 'count': len(self) }