def _add_payment(self, payment=None):
"""
Add a line with a new extra payment.
:param payment (tuple(str, float)): Extra payment for a month.
"""
self._table_widget.insertRow(self._table_widget.rowCount())
current_row = self._table_widget.rowCount() - 1
if payment:
month = QDate.fromString(payment[0], conf.DATE_FORMAT)
amount = payment[1]
else:
month = QDate.currentDate()
amount = 0.0
month_edit = QDateEdit(month)
month_edit.setDisplayFormat(conf.DATE_FORMAT)
month_edit.currentSection = QDateTimeEdit.MonthSection
self._table_widget.setCellWidget(current_row, 0, month_edit)
self._table_widget.setItem(current_row, 1,
QTableWidgetItem(str(amount)))
