import sys
from PySide2.QtWidgets import QApplication, QVBoxLayout, QDialog, QTableWidget, QHeaderView
from PySide2.QtCore import QRegExp
from PySide2.QtGui import QRegExpValidator

def regex_validator(regex):
    regex_expression = QRegExp(regex)
    regex_validator = QRegExpValidator(regex_expression)

    return regex_validator


class Form(QDialog):
    def __init__(self, parent=None):

        super(Form, self).__init__(parent)
        self.grid = QTableWidget(self)
        self.layout = QVBoxLayout()

        self.layout.addWidget(self.grid)
        self.setLayout(self.layout)
        self.table_settings()


    def table_settings(self):
        column_size = [100, 150, 100, 100]
        column_labels = ["A", "B", "C", "D"]

        self.grid.setColumnCount(len(column_size))
        self.grid.setRowCount(10)
        self.grid.verticalHeader().setVisible(True)
        self.grid.horizontalHeader().setSectionResizeMode(3, QHeaderView.Stretch)
        for cnt, column in enumerate(column_size):
            self.grid.setColumnWidth(cnt, column)

        row_labels = []
        for i in range(10):
            row_labels.append(str(i + 1))

        self.grid.setHorizontalHeaderLabels(column_labels)
        self.grid.setVerticalHeaderLabels(row_labels)
        self.grid.setFixedWidth(sum(column_size))

        regex = regex_validator(r'(\d+\.{1}\d+|\d+)')

#         do something to add the regex to the cells of column 0 and 2?!


if __name__ == '__main__':
    app = QApplication(sys.argv)
    ex = Form()
    ex.show()
    sys.exit(app.exec_())