Python tkinter 清除标签文本

Question

I have just started utilizing Python's tkinter module to create some basic GUIs. In the GUI shown below, the user is prompted to select an oil index and subsequent pricing information will appear (the price information is web scraped). However, I have not found a convenient way to clear the pricing label text for when the user selects another oil index. I have the full code attached below. Any suggestions would be greatly appreciated. Thank you.

# Import Python Modules
from tkinter import *
from ttk import *
import urllib2
from bs4 import BeautifulSoup
import re

# Generate Basic Window
root = Tk()
root.geometry("225x125")
root.resizable(0,0)
root.title("Global Oil Price GUI")

# Functions
def fetchdata(event):

    index = combo.current() # Get index of combobox selection
    # Obtain HTML
    url = 'http://oilprice.com/oil-price-charts/45' # URL to be scraped
    content = urllib2.urlopen(url)
    parsed = BeautifulSoup(content,'html.parser')

    # Parse HTML
    oilprice = parsed.findAll('td',attrs = {'class': 'last_price'})
    change = parsed.findAll('td',{'class':['change_up flat_change_cell','change_down flat_change_cell','change_up','change_down']})
    change_percent = parsed.findAll('td',{'class':['change_up_percent percent_change_cell','change_down_percent percent_change_cell','change_up_percent','change_down_percent']})

    # Pre-Initialize Arrays
    oilprice_extract = []
    change_extract = []
    change_percent_extract = []
    time_extract = []

    # Loop and Extract Text
    for ele_price, ele_change, ele_change_percent in zip(oilprice,change,change_percent):
        oilprice_extract.append(float(ele_price.text))
        change_extract.append(ele_change.text)
        change_percent_extract.append(ele_change_percent.text.split('%')[0] + '%')
        time_extract.append(re.sub('\n\t',' ',ele_change_percent.text.split('%')[1]))

    # Fill Field Based Upon Selection
    price_label = Label(root,text = oilprice_extract[index]).grid(row = 2,column = 2)
    change_label = Label(root,text = change_extract[index]).grid(row = 3,column = 2)
    change_percent_label = Label(root,text = change_percent_extract[index]).grid(row = 4,column = 2)
    update_label = Label(root,text = time_extract[index]).grid(row = 5,column = 2)

# Driver Code
combo_label = Label(root,text = "Futures & Indexes",justify = LEFT).grid(row = 0, column = 0)
combo = Combobox(root,values = ["WTI Crude","Brent Crude","Mars US","OPEC Basket","Canadian Crude Index"],width = 17)
combo.grid(row = 1, column = 0)
combo.bind("<<ComboboxSelected>>",fetchdata)

price_display = Label(root,text = " Price (USD):").grid(row = 2,column = 0)
change_display = Label(root,text = "Change:").grid(row = 3,column = 0)
change_percent_display = Label(root,text = "Change Percent:").grid(row = 4,column = 0)
update_display = Label(root,text = "Last Updated:").grid(row = 5,column = 0)

root.mainloop() # Run window continuously**

Update: Still a slight problem.
Scenario: User selects WTI Crude as first choice which shows: 'Last Update: (11 Minutes Delay)'

User then selects Mars US which should show something like 'Last Update: (2 Days Delay)'

Problem: The labels overlap each other as shown in this photo EXAMPLE PHOTO Any solution to this?

Answer 1

Clearing Label Text:

as jasonharper said. Use label.config(text="something")

The following script shows an example, where a label is dynamically incremented by 1 until the stop button is pressed:

import tkinter as tk

counter = 0 
def counter_label(label):
  def count():
    global counter
    counter += 1
    label.config(text=str(counter))
    label.after(1000, count)
  count()


root = tk.Tk()
root.title("Counting Seconds")
label = tk.Label(root, fg="green")
label.pack()
counter_label(label)
button = tk.Button(root, text='Stop', width=25, command=root.destroy)
button.pack()
root.mainloop()

reference: https://www.python-course.eu/tkinter_labels.php

labels overlap:

you shouldn't recreate label over and over again.

Besides, I think the following example will be better.

from tkinter import *
from tkinter.ttk import *
import requests
from tkinter.ttk import Combobox
from bs4 import BeautifulSoup, SoupStrainer
# import re  # As long as you can make do with str.replace(), you should use it instead of re.sub.


class CQueryOil(Tk):

    def __init__(self, query_country: list):
        super().__init__()  # init Tk
        self.__url = 'http://oilprice.com/oil-price-charts/45'
        self._query_country = query_country
        self._intvar_price = IntVar()
        self._strvar_change = StringVar(value='')
        self._strvar_change_percent = StringVar(value='')
        self._strvar_update_time = StringVar(value='')
        self.init_ui()

    @property
    def url(self):
        return self.__url

    @property
    def query_list(self):
        return self._query_country

    def run(self):
        self.mainloop()

    def init_ui(self) -> None:
        self.geometry("225x125")
        self.resizable(0, 0)
        self.title("Global Oil Price GUI")
        [self.grid_columnconfigure(col, weight=1) for col in (1, 2)]

        n_padx = 5
        Label(self, text="Futures & Indexes", justify=LEFT).grid(row=0, column=0, padx=n_padx, sticky='w')
        combo = Combobox(self, values=self.query_list, width=17)
        combo.grid(row=1, column=0, padx=n_padx, columnspan=2, sticky='w')
        combo.bind("<<ComboboxSelected>>", lambda event: self.update(event, combo=combo))

        for cur_row, label_name in enumerate(['Price (USD):', 'Change:', 'Change Percent:', 'Last Updated:']):
            Label(self, text=label_name, width=14).grid(row=2 + cur_row, column=0, padx=n_padx, sticky='e')

        Label(self, textvariable=self._intvar_price).grid(row=2, column=1, sticky='w')
        Label(self, textvariable=self._strvar_change).grid(row=3, column=1, sticky='w')
        Label(self, textvariable=self._strvar_change_percent).grid(row=4, column=1, sticky='w')
        Label(self, textvariable=self._strvar_update_time).grid(row=5, column=1, sticky='w')

    def update(self, event, combo) -> None:
        resp = requests.get(self.url)
        if resp.status_code != 200:
            return

        filter_data = SoupStrainer('tr', attrs={'class': ['stripe show_graph', 'stripe show_graph update_on_load']
                                                # 'data-id': ['45', '46', '50', '29', '68']
                                                })
        parsed = BeautifulSoup(resp.text, 'lxml', parse_only=filter_data)

        idx = combo.current()  # Get index of combobox selection
        try:
            dst_td_tags = parsed.find('td', string=self.query_list[idx]).find_next_siblings()
        except:
            import traceback
            print(traceback.format_exc())
            raise NameError(f'====Must match the data on the web page. Name:{self.query_list[idx]}=====')  # literal format Py3.6↑
        dst_list = [td.text for td in dst_td_tags]

        price, change, change_percent, update_time = dst_list
        change_percent = change_percent.split('%')[0]  # As long as you can make do with str.replace(), you should use it instead of re.sub.
        update_time = update_time.replace('\n\t', ' ')
        change_percent = change_percent
        update_time = update_time

        self._intvar_price.set(price)
        self._strvar_change.set(change)
        self._strvar_change_percent.set(change_percent)
        self._strvar_update_time.set(update_time)


if __name__ == '__main__':
    obj = CQueryOil(["WTI Crude", "Brent Crude", "Mars US", "Opec Basket", "Canadian Crude Index"])  # Must match the data on the web page
    obj.run()

Answer 2

The correct way is to use a StringVar to set the initial value of the Label , then you just need to call the .set() method of the StringVar instance you want to update.

Example:

price_str = StringVar()
prica_label = Label(root, textvariable=price_str).pack()
price_str.set("new price")