清除 tkinter 条目小部件中的文本

Question

我正在使用 Tkinter 条目小部件来允许用户将文本输入到 GUI。条目小部件具有默认文本，我想通过按一下按钮清除它们。我有以下代码：

from Tkinter import *

def delete_entries(fields):
  for field in fields:
    field.delete(0,END)

def UserInput(status,name):
  optionFrame = Frame(root)
  optionLabel = Label(optionFrame)
  optionLabel["text"] = name
  optionLabel.pack(side=LEFT)
  var = StringVar(root)
  var.set(status)
  w = Entry(optionFrame, textvariable= var)
  w.pack(side = LEFT)
  optionFrame.pack()

if __name__ == '__main__':
  root = Tk()
  fields = 'ExperimentNumber', 'OutputFileName', 'npts1', 'block1'    
  ExperimentNumber = UserInput("1", "Experiment number")
  OutputFileName = UserInput("output.txt", "Output file name")
  npts1 = UserInput("1000", "Number of points")
  block1 = UserInput("8", "Block size")

  Delete_button = Button(root, text = 'Clear all', command = delete_entries(fields))
  Delete_button.pack()

我尝试fields使用要删除的变量列表（如上）创建并在函数中迭代它delete_entries()，但是这会返回错误，因为字段中的条目是字符串。我曾尝试用fields = ExperimentNumber例如替换字段，但这会返回错误，因为还没有定义 ExperimentNumber。最后我尝试放入ExperimentNumber删除功能即

def delete_entries():
      ExperimentNumber.delete(0,End)

但这不起作用，因为ExperimentNumber有属性NoneType（我不明白为什么会这样，因为delete_entries()直到ExperimentNumber通过函数创建 Entry 小部件之后才会调用该函数UserInput）。如何删除 Entry 小部件中的所有文本？我的实际代码中有大约 20 个这样的内容，并且希望用户能够一键清除所有字段。

Answer 1

你在正确的轨道上，但你错过了两件小事。我在您的代码中添加了这两个并尝试用注释进行解释。

from Tkinter import *

def delete_entries():
  for field in fields:
    field.delete(0,END)

def UserInput(status,name):
  optionFrame = Frame(root)
  optionLabel = Label(optionFrame)
  optionLabel["text"] = name
  optionLabel.pack(side=LEFT)
  var = StringVar(root)
  var.set(status)
  w = Entry(optionFrame, textvariable= var)
  w.pack(side = LEFT)
  optionFrame.pack()
  return w
  #this return is crucial because if you don't return your widget's identity,
  #you can not use them in another function

if __name__ == '__main__':
  root = Tk()    
  ExperimentNumber = UserInput("1", "Experiment number")
  OutputFileName = UserInput("output.txt", "Output file name")
  npts1 = UserInput("1000", "Number of points")
  block1 = UserInput("8", "Block size")
  #you are saying it does not work because of they are strings.
  #then don't assign strings to fields. assign variables.
  fields = ExperimentNumber, OutputFileName, npts1, block1
  #since fields is defined in global scope, you don't need to use it as parameter

  Delete_button = Button(root, text = 'Clear all', command = delete_entries)
  Delete_button.pack()

  root.mainloop()