我有以下代码（python2.7）：

def btnGoClick(p1):
    params = w.line.get()
    if len(params) == 0:
        return

    # create child window
    win = tk.Toplevel()
    win.title('Bash')
    win.resizable(0, 0)
    # create a frame to be able to attach the scrollbar
    frame = ttk.Frame(win)
    # the Text widget - the size of the widget define the size of the window
    t = tk.Text(frame, width=80, bg="black", fg="green")
    t.pack(side="left", fill="both")
    s = ttk.Scrollbar(frame)
    s.pack(side="right", fill="y")
    # link the text and scrollbar widgets
    s.config(command=t.yview)
    t.config(yscrollcommand=s.set)
    frame.pack()

    process = subprocess.Popen(["<bashscript>", params], shell=False,
        stdout=subprocess.PIPE, stderr=subprocess.STDOUT)

    while True:
        out = process.stdout.readline()
        if out == '' and process.poll() is not None:
            break
        print out
        t.insert(tk.END, out)

“ longrunning” bash脚本的输出是实时捕获的（显示在控制台中），但是Tkinter窗口仅在子进程结束后显示！

如何在子进程启动之前实时显示窗口并更新其内容？