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13. Newspaper delivery revisited

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14. Repeat

Often, we will find that we want to repeat a series of instructions a fixed number of times. There is a way in Python to do so ... but it has too many new concepts to explain at this time. I will just show you the code, and immediately introduce repeat, a simpler replacement for it, unique to Reeborg’s World. The standard way is known as a for loop and is written as follows:

for i in range(n):
    # some
    # instructions
    # here


Using repeat will not work in Python programs meant to be run outside of Reeborg’s World. A loop is a block of instructions that is repeated.

In Reeborg’s World, we can write a repeat loop as follows:

repeat n:    # "n" is a whole number
    # some
    # instructions
    # here

For example, the following code will make Reeborg trace a square:

repeat 4:

By using repeat, we can rewrite some function definitions without having to repeat instructions:

def turn_right():
    repeat 3:

So, by using repeat we have yet another way to eliminate repetitions in our code.

Try it!

Change your program for the newspaper problem so that you use repeat wherever it would shorten the code. If you did not save it, go back to the previous lesson and redo it using repeat.

For educators

My reason for having repeat as an addition to Python’s standard notation was to avoid having to introduce 4 concepts at the same time (loops, variables as in _ in for _ in range(n), builtin functions like range as well as the concept of function arguments).

By design the n in repeat n must be an integer literal; it cannot be a variable. When students learn about variables, they should learn the proper Python syntax to do loops and forget about the non-standard repeat.