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In this exercise

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you're going to write a program that calculates the sum

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of all the even numbers from 1, to a particular number.

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So in the Input we're going to put in a particular number

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and then the code is to go through starting from 1,

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finding all the even numbers between 1

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and the Input number, and then adding them all together.

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In order to make sure

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that the code doesn't take too long to run,

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we are making sure the inputs don't go beyond 1,000

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because you might be sitting here for ages.

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So make sure that you put in the input as a small number

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like less than a hundred, or at least less than a thousand.

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The longer it is, the longer your code is going to take to run.

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But make sure that your code achieves its functionality.

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Check the Description pane,

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take a look at the Example Inputs

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and expected Example Outputs,

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and see if you can figure out how to do this

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using any Python function that you can come across

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but also using all of the basic skills

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in Python programming that you already have.

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And as a hint, you might want to look up the range() function

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to help you complete this exercise.

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Now, there are a number of ways of achieving this

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and I've included two in the complete solution

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but let's go through the first one.

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We start off with a variable called even_sum,

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and we set it equal to 0.

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This is going to be our accumulator.

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We're going to use this variable to add to it

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and be able to get the final sum.

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Now, how are we going to accumulate into it?

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Well, we're going to use a for loop

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to loop through each of the numbers in the range,

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starting from 2, which is the first even number after 1.

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So remember, we're looking for all the even numbers

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between 1 and our target number.

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And the range() function takes a starting point,

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an ending point,

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and an increment, similar to our traditional for loop,

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which you might have come across

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if you've learned the C programming language

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or other older programming languages.

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Essentially, we can provide three inputs

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through the range() function start, end,

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and the increment that we're going to go by each time.

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Now you can read upon the Python range() function

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but essentially what we're doing here

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is we're creating a for loop,

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and we're creating a range,

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starts from 2, ends at the target + 1.

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And the reason why it ends at target + 1

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is because the range will stop just before the end.

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So if your target was say, 100,

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then range will give you a range of numbers

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starting from 2 up until 99.

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So we have to modify that by adding 1

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if we want to include the target number in this range.

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So 2 comma and then target + 1,

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and then the final number is how much we want to add

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to the starting number each time.

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So what is the gap between each number.

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Because we want all the even numbers,

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each time we're going to add 2,

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and then we're going to loop through

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each of the numbers in that range.

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I recommend, if this is confusing at all,

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to simply just print out what that range creates

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and then change each of the inputs in the range

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and then making sure you understand how it works.

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But once you understand it, it's actually pretty simple,

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we're looping through each of the numbers

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in this artificial range that we've created,

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and then we simply add each of the numbers

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that's in that range to each other

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and we end up with the sum of all the numbers in that range,

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and then we can simply print it out.

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In the second method of completing this coding exercise,

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and believe me, there's way more

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than two ways of achieving this,

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this is just another one I want present you with.

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In this case, we're creating a range

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that just has a start and an end.

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Now, when we don't specify the increment,

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the third value in the range function,

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then it's going to increment by 1.

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So we start at 1 and we end our range at target + 1

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to include the target, not go above the target,

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that's just the peculiarity of how range works,

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and then we loop through the range,

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and then we use our even checker

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which we've created before, by using the modulo (%).

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So we say if the number we're currently looping through,

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modulo 2 is equal to 0,

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then it's cleanly divisible by 2,

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therefore it must be even, in that case,

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we're going to add this number to our alternative_sum

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to accumulate the numbers that are even.

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And then finally, we print it out.

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So if you created a different program but yet it still works

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and you managed to use a for loop, then congratulations.

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That's all I wanted to see.

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Now, very often as you're programming

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you might have certain needs that you might want to

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be able to get the sum of all the numbers

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in a list or the maximum of all the numbers in the list.

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Now, if you have a quick Google around

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and you can't find a good way of doing it,

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a simple way like the len() function or the sum() function,

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then you know that you can always just write it yourself.

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But if you do look for it

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and you find something, for example,

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in this case the range() function,

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and you do want use it,

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then it can often save you a lot of time.

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So there are lots of options

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and there are more options when you have more skills.

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So hopefully this exercise worked out for you.

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If not, be sure to go back and modify your code as needed.