위젯에서 그런기능이 제공 안되네요.

테이블위젯에 keypressevent 등록하고 ctrl+c 일때 항목을 복사하여 클립보드에 넣어주는 형태로 구현해야 합니다.

테스트해본 예제를 올려드립니다.

import sys
import io
import csv
from PyQt5.Qt import *
from PyQt5.QtCore import *
from PyQt5.QtWidgets import *

data = {'col1':['1','2','3'], 'col2':['4','5','6'], 'col3':['7','8','9']}

class MyTable(QTableWidget):
    def __init__(self, data, *args):
        QTableWidget.__init__(self, *args)
        self.data = data
        self.setmydata()
        self.resizeColumnsToContents()
        self.resizeRowsToContents()
        self.setSelectionMode(QAbstractItemView.ExtendedSelection)

    def setmydata(self):

        horHeaders = []
        for n, key in enumerate(sorted(self.data.keys())):
            horHeaders.append(key)
            for m, item in enumerate(self.data[key]):
                newitem = QTableWidgetItem(item)
                self.setItem(m, n, newitem)
        self.setHorizontalHeaderLabels(horHeaders)

    def keyPressEvent(self, ev):
        if (ev.key() == Qt.Key_C) and (ev.modifiers() & Qt.ControlModifier): 
            self.copySelection()

    def copySelection(self):
        selection = self.selectedIndexes()
        if selection:
            rows = sorted(index.row() for index in selection)
            columns = sorted(index.column() for index in selection)
            rowcount = rows[-1] - rows[0] + 1
            colcount = columns[-1] - columns[0] + 1
            table = [[''] * colcount for _ in range(rowcount)]
            for index in selection:
                row = index.row() - rows[0]
                column = index.column() - columns[0]
                table[row][column] = index.data()
            stream = io.StringIO()
            csv.writer(stream).writerows(table)
            QApplication.clipboard().setText(stream.getvalue())


def main(args):
    app = QApplication(args)
    table = MyTable(data, 5, 3)
    table.show()
    sys.exit(app.exec_())

if __name__=="__main__":
    main(sys.argv)