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- [Speaker] In this video
we're going to take a look

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at a script example that
processes a dictionary

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of student grades.

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Now the script we'll be
looking at is fig06_01.py

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And I'm just going to
go ahead and run it here

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so you can see the results of the script.

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On a student by student basis

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we're going to calculate
that student's average

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for the class.

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And we'll format that

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with two digits to the
right of the decimal point.

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And then for the entire class

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we're also going to
calculate the class average.

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So now that we've seen
the output of the script

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let's jump over to a text editor here

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and take a look at the script itself.

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Now once again we always start our scripts

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with a comment showing you the file names

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so that you can find them in the files

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that are associated with these videos.

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And as always you should start your script

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with a doc string that specifies
the purpose of the script.

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And depending on how
complex your script is

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that doc string may be
more complex as well.

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Now the key part of this example

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is of course our dictionary.

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The great book.

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And because it's a little
bit more complex dictionary

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I put it across multiple
lines of code here

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in the script.

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So it's not uncommon to see
people line up the curly braces

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like you see here.

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And it's not uncommon for them

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to put individual key
value pairs one per line

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for readability in their code.

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In this case we have
keys, which are strings

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the students names

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and we have values which are list objects

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which in turn contain other values.

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And those list objects of course

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are mutable as well

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although we won't modify
them in this example.

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So on a student by student basis

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what we're going to do
down below in a loop

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is pick off one key value pair at a time.

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Sum up the grades in the list.

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Display the students name
and average for those grades.

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And then keep track of the total

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of all the grades we've seen so far

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and the number of grades we've seen so far

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so that when the loop is done

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we can calculate the class average.

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So along those lines we've
created a couple of variables

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both initialized to zero here.

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Where we'll keep track of
the total of all the grades

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and account of all the grades.

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And here is the for loop

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that's going to process
that dictionary up above.

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So of course we've already seen previously

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gradebook.items is going

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to give us back something
that we can iterate over

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that gives us two bulls containing

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the keys and the values.

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One key value pair at a time.

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We're going to unpack that two bull

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into name for the key

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and grades for the list of grades

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that's the associated value.

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Once we have that we
can sum up those grades

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simply by handing the list
to the built in sum function.

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Again that's one of those

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python functional style reductions

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that's built into the language.

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You give it a sequence of values

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it gives you back the sum of those values.

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We store that here in total.

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We'll use that down below
as well a couple of times.

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In this print statement here

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we have a formatted string that consists

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of the name of the student

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and another place holder over here

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where we'll display the average

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and notice the calculation being performed

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which is the total

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divided by the length
of that grades array.

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So that'll give us our class average

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and we decided we'd like to format that

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as a floating point number

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with two digits to the
right of the decimal point.

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Don't forget that the division operator

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always gives you a floating point result.

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Now once we've displayed the information

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for the current student

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we then take that
students total and add it

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to the all grades total.

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And we take the length of the grades array

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and add that to the all
grades count as well.

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And as you can see down here

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after the loop completes we
have another print statement

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that's going to output
the classes average is

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and notice we have a single
quote character in the strings.

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So we delineated this string
with double quote characters.

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And the place holder performs another one

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of those average calculations.

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This time with all grades
total and all grades count.

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And formatted once again with two digits

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to the right of the decimal point.