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Section 7.6 Looping and counting

The following program counts the number of times the letter “r” appears in a string:
This program demonstrates another pattern of computation called a counter. The variable count is initialized to 0 and then incremented each time an “r” is found. When the loop exits, count contains the result: the total number of rs.

Activity 7.6.1.

11-9-2: What is printed by the following: 
s = "peanut butter"
count = 0
for char in s:
    if char == "t":
          count = count + 1
print(count)
  • 0
  • Incorrect! count is initialized to 0, but is then incremented by the for loop. Try again.
  • 3
  • Correct! The letter t appears 3 times in "peanut butter".
  • 4
  • Incorrect! The value of count is initially 0, not 1. Try again.
  • Nothing, this is an infinite loop
  • Incorrect! This for loop will eventually terminate because string s has a finite number of characters. Try again.

Activity 7.6.2.

There are four errors in the following code. Fix the function so it takes a string and a character as arguments and returns the count of the character within the string.
Solution.
To fix the function, ensure that the four syntax or logic errors are corrected: properly initialize the count variable to 0, use the correct loop syntax to iterate through the string, check for equality using the == operator, and properly increment the count before returning the final total.
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