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This is the solution of the two previous

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exercises, and so let's start with the first one.

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I'm going to create a new file. So a New, Python

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File, actually, let's name it compute_average_from_list,

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and say from_file to make it different

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from the previous one. So first, I'm going to need

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to read a list of numbers from the file. Let's use

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the file_test. So we have six numbers here, and I'm

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going to compute the average from those. So we're

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going to start with, so the with keyword open, and

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then file_test, gonna use the relative path, r

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because we want to read from the file, and then as

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f:, okay, and I'm going to do for line in f, okay,

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and I'm going to put each number that I get from

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each line, okay, inside a new list, and I'm going

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to create here, a number_list. So an empty list.

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And here, I am going to do number_list.append,

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to add a new element to that list, line.rstrip

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without the backslash character here. The

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thing is that this is going to add a string, okay,

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to the list, what I want is to add a number. So I

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could cast it to an integer, okay, or float number

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as you want. And we've to cast it to float, like

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this. So this is going to add a float number in

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the number_list. And then after this, I have

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actually, I have my number_list with all the

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numbers here. So let's print actually a number_list,

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and what I'm going to do now is to compute

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the average. So to compute the average, I'm going

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to go back to that file here compute_list_average,

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and instead of just copying this function

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inside that file, I'm simply going to, to copy

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this function inside the my_computations module.

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Okay, I add the function here. So now I have two

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functions in my module. And then in this file,

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where I want to compute the average, I'm going to

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add a new line at the top, which is from my_computations

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import compute_list_average. And

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as you can see here, also, when it's gray on PyCharm,

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it means that you are not using the imports,

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okay, and it's going to turn into a different

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color when you start to use it. And I'm going to

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do print(compute_list_average). So still using

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the auto completion from the number_lists, so I

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don't need to write the function again, here, I

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don't need to copy it, I just need to import it

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from the module. And now if I run this, so run

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with compute_average_from_list_from_file, you can see

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we have the list here with the six values, and

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then the average right after that. Okay, and

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this is the solution for the exercise number two.

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So I have created here a list that you are going

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to be able to download unordered_cities.txt. So

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for once I have added an extension, okay, so you

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can add an extension or not, it doesn't really

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matter. Okay, so 10 cities, 10 Random cities that

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are not sorted alphabetically, as you can see. So

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I'm going to create a new Python file, let's say

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sort_cities. Okay. So I'm going to read first all

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the cities here and put them in a list. So city_list

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is an empty list. I'm going to the with open

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unordered_cities,

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I can use the auto completion here with

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r because we want to read, okay, from the file as

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f and when to do for line in f. So as you can see,

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that's always the same structure, okay. city_list.append,

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and then I'm going to do line.rstrip

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backslash n. So again, that's always the

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same thing here. And now so this is a string I

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added to a list, which contains strings, so the

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datatype is correct. And now I'm going to sort the

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list I'm going to create a new list named sorted_city_list

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is equal to and then sorted function

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with the city_list. This is going to return the

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sorted version of that list and I put that in a

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new variable or a new list here, sorted_city_list.

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If you want, you can also print the intermediate

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result to see how is it working. And I'm going to

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create a new file or just write to a new file,

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that new list I have created here. So with open

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and we're going to create a file named unordered_cities.txt,

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okay, and I'm going to use w for

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write get as f. And now what I'm going to do is

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I'm going to put each cities okay from this new

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list, okay, in a different line. So I'm going to

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do for city in sorted_city_list. So

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make sure you do a follow up on that list and not

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that list. Otherwise, you're not going to change

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the order in the file. So for each city I have,

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I'm going to write it in a new line. So I'm going

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to do f.write, city, and if I do that, it's

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just going to add all the cities together in the

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same line. So I'm going to do plus quotes, quotes

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and backslash n to add a new line character. This

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way I can write each element from this array from

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this list on a new line. That's also a very common

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structure, you're going to use many times and well

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that's it, I'm simply going to do print down Okay,

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so it's always nice to have down or okay, at the

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end of a Python script, so you can know when this

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is finished, okay. And now ran. So cities, you can

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see done and well you can see on the left, we have

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so we have an ordered series here. And we have

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other cities, okay, this is a new text file, which

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also contains density, but these time

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alphabetically ordered.