Python #4: The “for” Loop

There’s another nice way to get the computer do do things a number of times: the “for” loop. This time, we get to specify exactly how many times we want the thing to happen. Try this little program:

The loop names a variable “i” and tells the computer to keep going, adding one each time, for ten repetitions. If you run the program, you’ll see it starts at zero and ends at nine. This is because the computer starts counting at zero. If we want to make it do one to ten we need to make a little change.

The  “range”  command lets us specify a start and end point, separated by commas. We can also tell the machine what steps to go in.

So, if I alter my program to this:

It will count down from 10 to 1 in steps of -1.




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