比较对象并在列表中搜索

Question

我使用 Python 3 和 PySide2（Qt for Python）（都是最新的）。我有一个 PySide2 对象列表，必须检查列表中是否存在某个项目。如果我尝试这样做，我会收到错误消息：

NotImplementedError: operator not implemented.

from PySide2 import QtGui
item = QtGui.QStandardItem()
item1 = QtGui.QStandardItem()

item == item1 # creates error

list1 = [item, item1]
item1 in list1 # creats error

我做错了什么？我怎样才能做到这一点？我必须自己实现“==”运算符吗？预先感谢您的帮助！

Answer 1

运算符==等价于__eq__。用法类似于 a.__eq__(b) 或 a == b。例外情况是 the class 没有实现该方法。

而且文档确实说：

Reimplement operator if you want to control the semantics of item comparison. operator determines the sorted order when sorting items with sortChildren() or with sort().

Answer 2

如评论中所述，您得到的错误是 bug 的一部分，它是 PySide 的残余。

我认为你有一个 XY problem, and what you want is to check if there is an item with a predefined text. If so, it is not necessary to implement the operator == but use the findItems() 方法：

from PySide2 import QtCore, QtGui

if __name__ == "__main__":
    import sys

    md = QtGui.QStandardItemModel()
    for text in ("Hello", "Stack", "Overflow"):
        md.appendRow(QtGui.QStandardItem(text))

    words = ("Hello", "World")

    for word in words:
        if md.findItems(word, flags=QtCore.Qt.MatchExactly, column=0):
            print(f"{word} exists")
        else:
            print(f"{word} not exists")

如果您想搜索其他角色，请使用match()方法：

from PySide2 import QtCore, QtGui

FooRole = QtCore.Qt.UserRole + 1000

if __name__ == "__main__":
    import sys

    md = QtGui.QStandardItemModel()
    for i, text in enumerate(("Hello", "Stack", "Overflow")):
        it = QtGui.QStandardItem(str(i))
        it.setData(text, FooRole)
        md.appendRow(it)

    words = ("Hello", "World")

    for word in words:
        if md.match(
            md.index(0, 0), FooRole, word, hits=1, flags=QtCore.Qt.MatchExactly
        ):
            print(f"{word} exists")
        else:
            print(f"{word} not exists")

比较对象并在列表中搜索

Compare objects and search in list

python

python-3.x

pyside2