/Python_PetStore4-5

Software 1 - Class Exercise 4

Goals

  • Use list functions

Instructions

Using List Functions

  1. In the ProductLogic class, in the constructor where you are creating a new list of products, instead of having that list be empty, go ahead and add 2 or 3 products to it. One of those products should have a quantity of 0.

  2. Add the method GetOnlyInStockProducts() which will end up returning a list.

  3. In the function definition of GetOnlyInStockProducts(), we are going to filter our product list to only return products with quantity greater than 0. We can the use the following example but you will need to change out someListOfThings with your product list. This will return a new list that contains only the products whose Quantity property is greater than zero.

    Example: list(filter(lambda theThing: theThing.Quantity > 0, someListOfThings))

    To explain the example a bit: We need to surround the filter() in list() so that it transform the filter result into a list. Additionally we are using a lambda as the first parameter of the filter() so it will execute the lambda on each item within someListOfThings similar to the behavior of a for loop. In our case it is checking the Quantity property of each item our list and evaluating whether it's greater than zero; if it is greater than zero than we are filtering that value.

  4. Let's take this a step further. Let's say we would only want to return the names of the products. We would do this by using the map() method. We will use this similarly to the Select() function which is found in C# and javascript. Even though python doesn't contain the Select() functions we can achieve the same behavior by using the map() function.

  5. Use map so that we get only the list of names by doing: list(map(lambda theThing: theThing.Name, ourProducts)).

    Explanation: The map() function is similar to filter() in that it will interact on every item of a given list. map() however will execute a certain function or expression on each item instead of filter()'s behavior.

    This is an example of using map to print each item in a list: map(lambda element: print(element), myList)

  6. Finally, add a UI option to view in stock products only.