# Day 22: Exercise Solutions Here are our solutions for the day 22 exercises in the 30 Days of Python series. Make sure you try the exercises yourself before checking out the solutions!

### §1) Below you'll find a list containing several tuples full of numbers. Use the `map` function to find the sum of the numbers in each tuple. Use manual iteration to print the first two results provided by the resulting `map` object.

``numbers = [(23, 3, 56), (98, 1034, 54), (254, 344, 5), (45, 2), (122, 63, 74)]``

First things first, lets create our `map` object. In this case we don't need anything complicated like a lambda expression or something from the `operator` module: we can just use the `sum` function.

``````numbers = [(23, 3, 56), (98, 1034, 54), (254, 344, 5), (45, 2), (122, 63, 74)]
totals = map(sum, numbers)``````

Now that we have a `map` object assigned to `totals`, we just need to pass this `map` object to `next` to get an item out of it. This is possible because `map` objects are iterators.

``````numbers = [(23, 3, 56), (98, 1034, 54), (254, 344, 5), (45, 2), (122, 63, 74)]
totals = map(sum, numbers)

print(next(totals))  # 82
print(next(totals))  # 1186``````

Note that the last three sums haven't been calculated at this point.

### §2) Write a program to create a schedule that lists which of your employees will lock up the shop on a given day over a 30 day period. You should list the day number, the employee name, and the day of the week.

For this exercise, we've been told that we have three employees that will take turns to lock up the shop each night. For example, if we start with employee A, they will close up on the first day, then employee B, followed by employee C. The cycle then starts over on day 4 with employee A.

In order to create this cycling behaviour we're going to be using a very useful function in the `itertools` module called `cycle`. `cycle` is a special type of iterator that will provide us an infinite number of results in some predefined sequence.

If we look at the documentation, we can see that the function signature looks like this:

``itertools.cycle(iterable)``

This tells us that `cycle` takes a single iterable which defines the values that should be cycled through.

With that in mind, let's import the module and create two `cycle` iterators: one for the employees, and one for the days of the week.

``````import itertools

employees = itertools.cycle(["Peter", "Fiona", "Carl"])
days = itertools.cycle(["Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday", "Sunday"])``````

Now that we have this, the rest of the solution is pretty simple. We just need to create a `for` loop that will have 30 iterations, which we can do by iterating over a `range`. We can then use the values in this `range` for the day numbers, and we can use `next` to keep grabbing values from the two cycles.

``````import itertools

employees = itertools.cycle(["Peter", "Fiona", "Carl"])
days = itertools.cycle(["Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday", "Sunday"])

for day_number in range(1, 31):
print(f"Day {day_number} ({next(days)}): {next(employees)} closes.")``````

One of the really nice things about a solution like this is that we can add or remove employees by just modifying the list we pass into the employees `cycle`. We don't have to make any other changes.

``````import itertools

employees = itertools.cycle(["Peter", "Fiona", "Carl", "Helen"])
days = itertools.cycle(["Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday", "Sunday"])

for day_number in range(1, 31):
print(f"Day {day_number} ({next(days)}): {next(employees)} closes.")``````

I think it would also be a good exercise to think about how you might do this without using any iterators.

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