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Sometimes when you run into errors in our code.

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It's not a syntax error.

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It's not a runtime error.

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It's just that the code doesn't quite do what it was that we had intended for it do.

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These things are often also caused by typos.

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So let's make a working copy of, incrange-errors.py and we will call that

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incrange-errors-working.py.

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This is our inclusive range method from another example in this course.

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There is the code, and you will see that it calls it down here, and we will just

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run it and see what happens.

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Well, nothing happens.

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That's not a good sign.

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So why would nothing happen?

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Well, what's supposed to happen?

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The object gets initialized and it gets constructed with these parameters,

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a start, a stop and a step of 4, 25 and 3, and then it gets printed out by

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using the object as an iterator, and we can see right here, here is the iterator function.

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It's go a yield here, which makes it a generator, so that looks like it should work.

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We have the start, stop and step, and so here is the start and the stop and the

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step, and let's just run through the code here and see what happens.

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I am starting here because this is where the print is, and this is also just the

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shortest and easiest to look at piece of code. I happen to know, because I wrote this,

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that this is a little bit more of a hornets nest, and so I am just going

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to start here because it looks like a simple place to start.

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This is where the action is actually happening here.

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So i equals start, while i is greater than or equal to and that doesn't look right,

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because the start is at 4, and the stop is at 25, so I would want to run

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this loop while i <= stop.

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So that looks like a typo, and so I will change that, and I will save it and run it,

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and now we are getting some output here.

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So let's look at the output and see if it is correct.

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So we have this range.

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It starts at 4 and over here we are starting at 3. That's not right.

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And it stops at 25. Okay, well, that's plausible, and the step is 3, so 3+3

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would be 6, 7+3 would be 10.

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This is actually stepping by 4.

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It's starting at 3 and stepping by 4.

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So it would appear that I got those 2 swapped some place.

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So let's look at the code and see how this works.

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So we have numargs, which is the length of args.

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So that's the number of arguments that I am passing in and if numargs is

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less than one, we have a TypeError. If numargs equals to one, so I have three arguments.

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So let's just step down here to numargs equals three and so I

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assign them like this.

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Step, stop and start equals args.

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Well, that's not right.

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Its start, stop and step is what it should be.

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So I will switch those. Those got swapped just like I thought. start, stop and step.

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And that looks like it should fix it. I will save that and run it, and here we

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have a different result.

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Let's see if this looks right.

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It should start at 4.

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It is starting at 4.

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Stop at 25, that looks right, and the step is 3. So we have 4,

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7, 10, 13, 16, that looks right.

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So now it's working as we expected.

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At this point I would test the other ways of passing parameters, test some

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other corner cases.

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I happen to know because I made these errors that that's the extent of

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the errors in the file.

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So the trick is like so much of debugging to be patient, to follow the execution

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of the code, to look at what's supposed to happen that's not happening, to look

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at what's happening that's not supposed to happen, and through patience and

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perseverance to find those little typos, and really the key here is the

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patience and perseverance.

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Sometimes this can just take a while.