7.3. Traversal through a string with a loop¶
A lot of computations involve processing a string one character at a
time. Often, they start at the beginning, select each character in turn,
do something to it, and continue until the end. This pattern of
processing is called a traversal. One way to write a
traversal is with a
This loop traverses the string and displays each letter on a line by
itself. The loop condition is
index < len(fruit), so when
index is equal to the length of the string, the condition
is false, and the body of the loop is not executed. The last character
accessed is the one with the index
len(fruit)-1, which is
the last character in the string.
while loop that starts at the last character in the string and works its way
backwards to the first character in the string, printing each letter on a separate line.
For reference, the CodeLens above shows an example of a word printed letter by letter.
Another way to write a traversal is with a
Each time through the loop, the next character in the string is assigned
to the variable
char. The loop continues until no
characters are left.