问题
So I have this program which requests a file from the web and the user can download it. I am using urllib.request and tkinter for my program. The problem is that when the user hits the 'Download' button there is no pause or cancel until the file gets downloaded and the program freezes too. I really want to create a pause or a cancel button, but I do not know how and I want to eliminate the freezing of the program. Should I use another library like 'requests'? Or should I try threading? Can someone guide me through this? My code(BTW if you know any way to improve my program I would appreciate it a lot if you shared it with me):
from tkinter import *
from tkinter import font as tkFont
import random
import urllib.request
import requests
from tqdm import tqdm
from tqdm.auto import tqdm
def printsth():
print("Yay it works! ")
def main_menu():
root = Tk()
# the top menu
num = IntVar()
# var = IntVar()
menu = Menu(root)
root.config(menu=menu)
submenu = Menu(menu)
menu.add_cascade(label="Settings", menu=submenu)
def custom_op():
custom = Tk()
custom.mainloop()
submenu.add_command(label="Customization ", command=custom_op)
def settings_op():
set_win = Tk()
set_win.mainloop()
submenu.add_command(label="Settings ", command=settings_op)
submenu.add_separator()
submenu.add_command(label="Exit", command=root.destroy)
# the edit menu
editmenu = Menu(menu)
menu.add_cascade(label="Edit", menu=editmenu)
editmenu.add_command(label="Redo...", command=printsth)
# the tool bar
toolbar = Frame(root, bg="light gray")
insert_button = Button(toolbar, text="Insert an image", command=printsth)
insert_button.pack(side=LEFT, padx=2, pady=2)
print_button = Button(toolbar, text="Print", command=printsth)
print_button.pack(side=LEFT, padx=2, pady=2)
toolbar.pack(side=TOP, fill=X)
# the download function
def download_image():
global formatname
if num.get() == 1:
name = random.randrange(1, 100000)
else:
name = str(name_entry.get())
formatname = str(format_entry.get())
'''if var.get() == 1:
operator = str(url_entry.get())
formatname = '.' + operator[-3] + operator[-2] + operator[-1]
else:
pass'''
fullname = str(name) + formatname
url = str(url_entry.get())
fw = open('file-size.txt', 'w')
file_size = int(requests.head(url, headers={'accept-encoding': ''}).headers['Content-Length'])
fw.write(str(file_size))
fw.close()
path = str(output_entry.get()) + "\\"
urllib.request.urlretrieve(url, path.replace("\\", "\\\\") + fullname)
# the status bar
status_bar = Label(root, text="Downloading...", bd=1, relief=SUNKEN, anchor=W)
status_bar.pack(side=BOTTOM, fill=X)
# the download frame
body_frame = Frame(root, bg="light blue")
download_button = Button(body_frame, text="Download! ", command=download_image, border=3, width=20, height=5)
download_design = tkFont.Font(size=12, slant='italic')
download_button['font'] = download_design
download_button.pack(side=LEFT, pady=5, padx=5)
body_frame.pack(side=LEFT, fill=Y)
# the main interaction menu
inter_frame = Frame(root)
url_entry = Entry(inter_frame)
label = Label(inter_frame, text="Enter the image URL: ")
file_format = Label(inter_frame, text="Choose your file format: ")
format_entry = Entry(inter_frame)
file_name = Label(inter_frame, text="File's name: ")
name_entry = Entry(inter_frame)
check_name = Checkbutton(inter_frame, text="Give a random name", variable=num)
# check_format = Checkbutton(inter_frame, text="Download with default format", variable=var)
output_path = Label(inter_frame, text="Choose output path: ")
output_entry = Entry(inter_frame)
file_name.pack(anchor=CENTER, expand=1)
name_entry.pack(anchor=CENTER, expand=1)
check_name.pack(anchor=CENTER, expand=1)
label.pack(anchor=CENTER, expand=1)
url_entry.pack(anchor=CENTER, expand=1)
file_format.pack(anchor=CENTER, expand=1)
format_entry.pack(anchor=CENTER, expand=1)
# check_format.pack(anchor=CENTER)
output_path.pack(anchor=CENTER, expand=1)
output_entry.pack(anchor=CENTER, expand=1)
inter_frame.pack(expand=1)
root.mainloop()
# the end!
main_menu()
回答1:
You can use reporthook option of urllib.request.urlretrieve() to associate a callback and abort the download by raising exception inside the callback:
downloading = False # flag to indicate whether download is active
def download_progress(count, blksize, filesize):
nonlocal downloading
if downloading:
downloaded = count * blksize
print('downloaded %s / %s' % (downloaded, filesize))
root.update() # let user interact with the GUI
else:
# user selects to abort the download
raise Exception('download aborted!')
# the download function
def download_image():
global formatname
nonlocal downloading
if downloading:
downloading = False
return
download_button.config(text='Stop!') # let user to click the button to abort download
downloading = True
if num.get() == 1:
name = random.randrange(1, 100000)
else:
name = str(name_entry.get())
formatname = str(format_entry.get())
'''if var.get() == 1:
operator = str(url_entry.get())
formatname = '.' + operator[-3] + operator[-2] + operator[-1]
else:
pass'''
fullname = str(name) + formatname
url = str(url_entry.get())
fw = open('file-size.txt', 'w')
file_size = int(requests.head(url, headers={'accept-encoding': ''}).headers['Content-Length'])
fw.write(str(file_size))
fw.close()
path = str(output_entry.get()) + "\\"
try:
urllib.request.urlretrieve(url, path.replace("\\", "\\\\")+fullname, download_progress) # added reporthook callback
except Exception as e:
print(e) # download aborted
else:
print('done')
download_button.config(text='Download!') # resume download button
The text of download_button is changed to Stop! after it is clicked so that user can click it again to abort the download. When the download is aborted/completed, its text is changed back to "Download!".
来源：https://stackoverflow.com/questions/61193811/how-to-cancel-or-pause-a-urllib-request-in-python