Answer
code
Work Step by Step
# 14.7 (Tkinter: Count the occurrences of each letter) Revise the preceding exercise to
# display a histogram for the result, as shown in Figure 14.6. You need to display a
# message in a message box if the URL does not exist.
import urllib.request
from tkinter import *
from tkinter import messagebox
LINE_WIDTH = 23
BASE = 550
def showResult():
try:
file = urllib.request.urlopen(url.get())
lines = file.read().decode()
counts = [0] * 26
countLetters(lines.lower(), counts)
cnvs.delete("data")
cnvs.create_line(10, BASE, 595, BASE, tag="data")
x = 12
for i in range(26):
cnvs.create_text(x + 2, BASE + 8, text=chr(i + ord('a')), tag="data")
cnvs.create_rectangle(x - 9, BASE - counts[i], x + LINE_WIDTH - 9, BASE, tag="data")
x += LINE_WIDTH
except IOError:
messagebox.showwarning("Analyze URL",
"URL " + url.get() + " does not exist")
def countLetters(lines, counts):
for line in lines:
for ch in line:
if ch.isalpha():
counts[ord(ch) - ord('a')] += 1
window = Tk() # Create a window
window.title("Occurrence of Letters") # Set title
frame1 = Frame(window) # Hold four labels for displaying cards
frame1.pack()
cnvs = Canvas(frame1, width=600, height=600)
cnvs.pack()
frame2 = Frame(window) # Hold four labels for displaying cards
frame2.pack()
Label(frame2, text="Enter a URL: ").pack(side=LEFT)
url = StringVar()
Entry(frame2, width=20, textvariable=url).pack(side=LEFT)
Button(frame2, text="Show Result", command=showResult).pack(side=LEFT)
window.mainloop() # Create an event loop
