python - pydicom 中的 ds.get() 和 ds.get_item() 有什么区别

Question

有谁知道 Pydicom 中这两种方法有什么FileDataset.get()区别FileDataset.get_item()？谢谢！

Answer 1

这两者在用户代码中都不经常使用。 Dataset.get相当于python的dict.get；它允许您在字典中请求一个项目，但如果该项目在数据集中不存在，则返回默认值。从数据集中获取项目的更常用方法是使用点表示法，例如

dataset.PatientName

DataElement或通过标签号获取对象，例如

dataset[0x100010]

Dataset.get_item是一个较低级别的例程，主要用于某些传入数据有问题时，需要在将“原始数据元素”值转换为python标准类型（int、float、string类型等）之前对其进行更正。

当与关键字一起使用时，Dataset.get()返回一个value，而不是一个DataElement实例。 Dataset.get_item总是返回一个DataElement实例或一个RawDataElement实例。

Answer 2

我想您的答案在这两个功能的源代码中。看起来像get()处理过的字符串以及作为输入的 DataElements。

def get(self, key, default=None):
        """Extend dict.get() to handle DICOM DataElement keywords.

        Parameters
        ----------
        key : str or pydicom.tag.Tag
            The element keyword or Tag or the class attribute name to get.
        default : obj or None
            If the DataElement or class attribute is not present, return
            `default` (default None).

        Returns
        -------
        value
            If `key` is the keyword for a DataElement in the Dataset then
            return the DataElement's value.
        pydicom.dataelem.DataElement
            If `key` is a tag for a DataElement in the Dataset then return the
            DataElement instance.
        value
            If `key` is a class attribute then return its value.
        """
        if isinstance(key, (str, compat.text_type)):
            try:
                return getattr(self, key)
            except AttributeError:
                return default
        else:
            # is not a string, try to make it into a tag and then hand it
            # off to the underlying dict
            if not isinstance(key, BaseTag):
                try:
                    key = Tag(key)
                except Exception:
                    raise TypeError("Dataset.get key must be a string or tag")
        try:
            return_val = self.__getitem__(key)
        except KeyError:
            return_val = default
        return return_val





def get_item(self, key):
        """Return the raw data element if possible.

        It will be raw if the user has never accessed the value, or set their
        own value. Note if the data element is a deferred-read element,
        then it is read and converted before being returned.

        Parameters
        ----------
        key
            The DICOM (group, element) tag in any form accepted by
            pydicom.tag.Tag such as [0x0010, 0x0010], (0x10, 0x10), 0x00100010,
            etc. May also be a slice made up of DICOM tags.

        Returns
        -------
        pydicom.dataelem.DataElement
        """
        if isinstance(key, slice):
            return self._dataset_slice(key)

        if isinstance(key, BaseTag):
            tag = key
        else:
            tag = Tag(key)
        data_elem = dict.__getitem__(self, tag)
        # If a deferred read, return using __getitem__ to read and convert it
        if isinstance(data_elem, tuple) and data_elem.value is None:
            return self[key]
        return data_elem