21.7: Looping and Counting
- Page ID
- 16990
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The following program counts the number of times the letter a
appears in a string:
word = 'banana' count = 0 for letter in word: if letter == 'a': count = count + 1 print count
This program demonstrates another pattern of computation called a counter. The variable count
is initialized to 0 and then incremented each time an a
is found. When the loop exits, count
contains the result—the total number of a
’s.
Exercise \(\PageIndex{1}\)
Encapsulate this code in a function named count
, and generalize it so that it accepts the string and the letter as arguments.
Exercise \(\PageIndex{2}\)
Rewrite this function so that instead of traversing the string, it uses the three-parameter version of find
from the previous section.