问GridBag布局中有grid控件和button控件，如何通过button修改grid的某个单元格？

###### python3.6

import wx

import wx.grid as gridlib

class BaiTan_Frame(wx.Frame):

def __init__(self, parent, title):

super(BaiTan_Frame, self).__init__(parent, title = title)

self.InitUI(None, 0, 0, None)

self.Centre()

self.Show()

def InitUI(self, n_grid, iRow, iCol, const):

panel = wx.Panel(self)

sizer = wx.GridBagSizer(0, 0)

panel.SetSize((1600, 1400))

self.SetSize((830,300))

# 开始设置表格 tc_grid

tc_grid = gridlib.Grid(panel)

tc_grid.CreateGrid(6, 8)# 设置表格行列数

sizer.Add(tc_grid, pos = (0, 0), span=(0, 6), flag = wx.ALL, border = 5)

tc_grid.SetRowLabelSize(120)# 固定列的宽度

# #=======================

tc_grid.SetColLabelSize(0)# 固定行的高度 隐藏

tc_grid.SetColLabelAlignment( wx.ALIGN_CENTRE, wx.ALIGN_CENTRE )# 行表头内容对齐方式

tc_grid.SetDefaultCellAlignment( wx.ALIGN_CENTRE, wx.ALIGN_TOP )# 表格内容对齐方式

if n_grid == 'tc_grid':

tc_grid.SetCellValue(iRow, iCol, const)

#=============

renderer = wx.grid.GridCellAutoWrapStringRenderer()

# 开始设置按钮

button1 = wx.Button(panel, label = "按钮1")

self.Bind(wx.EVT_BUTTON, self.button1_Click, button1)

button2 = wx.Button(panel, label = "按钮2" )

self.Bind(wx.EVT_BUTTON, self.button2_Click, button2)

buttonExit = wx.Button(panel, label = "退出" )

self.Bind(wx.EVT_BUTTON, self.buttonExit_Click, buttonExit)

sizer.Add(button1, pos = (2, 0),flag = wx.ALL, border = 5) # pos 与位置有关

sizer.Add(button2, pos = (2, 1), flag = wx.ALL, border = 5) # pos 与位置有关

sizer.Add(buttonExit, pos = (2, 5),flag = wx.ALL, border = 5) # pos 与位置有关

panel.SetSizerAndFit(sizer)

def button1_Click(self, event):

self.InitUI('tc_grid', 2, 4, 'Python')

def button2_Click(self, event):

self.InitUI('tc_grid', 3, 5, '你好')

def buttonExit_Click(self, event):

self.Close(True)

app = wx.App()

BaiTan_Frame(None, title = 'GridBag Demo')

app.MainLoop()

######

#按钮1显示 "Python" ，按按钮2会显示 "你好" 但会擦掉 "Python"，反之亦然

怎么通过button修改grid的某个单元格而不影响其它单元格的内容