如何在QDoubleSpinBox中输入负浮点数？附实现代码与解决方案

问题背景 #

需要在QDoubleSpinBox组件中输入负浮点数，最初查阅文档未找到直接方法，于是编写了自定义的CustomDoubleSpinbox类及ComboBoxDelegate委托类来实现功能，后续发现通过内置方法即可轻松解决。

最初的自定义实现代码 #

from PyQt5.QtWidgets import QStyledItemDelegate, QLineEdit, QComboBox, QDoubleSpinBox, QModelIndex
from PyQt5.QtCore import Qt

class ComboBoxDelegate(QStyledItemDelegate):
    """A delegate that allows the user to change integer values from the model
       using a spin box widget. """

    def __init__(self, parent=None):
        super().__init__(parent)

    def createEditor(self, parent, option, index : QModelIndex):
        if index.column() == 0 :
            editor = QLineEdit(parent)
            return editor
        
        if index.column() == 1 :
            combo = QComboBox(parent)
            combo.addItems(["len","diam","conc"])
            editor = combo
            return editor
        
        if index.column() > 1 :
            editor = CustomDoubleSpinbox(parent)
            editor.setDecimals(3)
            return editor

    def setEditorData(self, editor , index):
        value = index.model().data(index, Qt.EditRole)
        if type(editor) == QComboBox :
            editor.setCurrentText(str(value))

        if type(editor) == CustomDoubleSpinbox :
            editor.setValue(value)

        if type(editor) == QLineEdit :
            editor.setText(value)

    def setModelData(self, editor , model, index : QModelIndex):
        if type(editor) == QComboBox :
            value = editor.currentText()
        if type(editor) == CustomDoubleSpinbox :
            editor.interpretText()
            value = editor.value()
        if type(editor) == QLineEdit :
            value = editor.text()
        model.setData(index, value, Qt.EditRole)

    def updateEditorGeometry(self, editor, option, index):
        editor.setGeometry(option.rect)

class CustomDoubleSpinbox(QDoubleSpinBox):
    def validate(self, text: str, pos: int) -> object:
        text = text.replace(".", ",")
        return QDoubleSpinBox.validate(self, text, pos)

    def valueFromText(self, text: str) -> float:
        text = text.replace(",", ".")
        return float(text)

更简洁的官方解决方案 #

无需编写自定义类，直接调用QDoubleSpinBox的setMinimum()方法，将最小值设置为负数即可支持输入负浮点数。示例代码：

# 假设spin_box是你的QDoubleSpinBox实例
spin_box.setMinimum(-float('inf'))  # 允许输入任意负数
# 也可设置具体最小值，例如
# spin_box.setMinimum(-100.0)

内容的提问来源于stack exchange，提问作者Thomas.C