9.12. Traversal and the
while loop can also control the
generation of the index values. Remember that the programmer is responsible for setting up the initial
condition, making sure that the condition is correct, and making sure that something changes inside the
body to guarantee that the condition will eventually fail.
The loop condition is
position < len(fruit), so when
position 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.
Here is the same example in codelens so that you can trace the values of the variables.
Check your understanding
- Yes, idx goes through the odd numbers starting at 1. o is at position 4 and 8.
- o is at positions 4 and 8. idx starts at 1, not 0.
- There are 2 o characters but idx does not take on the correct index values.
strings-12-1: How many times is the letter o printed by the following statements?
s = "python rocks" idx = 1 while idx < len(s): print(s[idx]) idx = idx + 2
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