Answer
code
Work Step by Step
# 14.5 (Tkinter: Count the occurrences of each letter) Revise the preceding exercise to
# display a histogram for the result, as shown in Figure 14.4. You need to display a
# message in a message box if the file does not exist.
from tkinter import * # Import tkinter
import tkinter.messagebox # Import tkinter.messagebox
from tkinter.filedialog import askopenfilename
LINE_WIDTH = 23
BASE = 350
def showResult():
file = open(filename.get(), 'r')
lines = file.readlines()
for i in range(len(lines)):
lines[i] = lines[i].lower()
counts = [0] * 26
countLetters(lines, 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
def countLetters(lines, counts):
for line in lines:
for ch in line:
if ch.isalpha():
counts[ord(ch) - ord('a')] += 1
def openFile():
filenameforReading = askopenfilename()
filename.set(filenameforReading)
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=400)
cnvs.pack()
frame2 = Frame(window) # Hold four labels for displaying cards
frame2.pack()
Label(frame2, text="Enter a filename: ").pack(side=LEFT)
filename = StringVar()
Entry(frame2, width=20, textvariable=filename).pack(side=LEFT)
Button(frame2, text="Browse", command=openFile).pack(side=LEFT)
Button(frame2, text="Show Result", command=showResult).pack(side=LEFT)
window.mainloop() # Create an event loop
