Strange behavior of Python + PySide. How to change data recursively in QSortFilterProxyModel()?

Question

Python

Hello! Help me to understand.
From model = QSqlTableModel()I receive the table with some quantity of fields.
Next, I put a filter on it:

def update_list(): тут пытаюсь заменить все значения "значение_1" на "значение_2" во второй колонке
    i = 0 #счетцик
    while i < model_list.rowCount():
      model_list.setData(model_list.index(i, 2), 'значение_2') в этом моменте происходит магия. см. ниже
      print ('счетчик ',i)
      i = i+1
    print ('количество строк',model_list.rowCount())
    model.select()
    print('Обновление')



  model_list = QSortFilterProxyModel()
  model_list.setSourceModel(model)
  model_list.setFilterCaseSensitivity(Qt.CaseInsensitive)
  model_list.setFilterKeyColumn(2)
  model_list.setFilterFixedString('значение_1') 
  update_list()

The output is some kind of heresy.
Not all values ​​change, but only half in random order.
What am I doing wrong? Maybe there is another way to change the values ​​in QSortFilterProxyModel() in one go?
PS The code may contain inaccuracies since this is not the first time I've tried to make it work.