Why do I have to repeat items in list slices in order to make this work?

[deanhystad]

Slicing starts at the start number and ends before the end number. I think this is because indexing starts at 0.

things = "abcdefg"
print(things[:3])  # Print the first 3 letters.

If the slice contained the ending value you would write this:

things = "abcdefg"
print(things[:2])  # Print the first 3 letters.

Hmmm. I want three values, but I need to ask for 2?

range() use the same protocol.

for i in range(3):  # I want to iterate 3 times
    print(i)

Output:
0
1
2

Similar to slicing, range would look odd if the range included the end number.

for i in range(2):  # I want to iterate 3 times.  Why do I need to enter 2?
    print(i)

When you start with zero, the number in range(number) equals the number of iterations. You can set the start number to any value, but by a huge margin most range(start, end, increment) skip setting the start and increment.