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Generator pipelines allow us to use multiple generators to perform a series of operations all within one expression. We can break down complex operations into smaller, more manageable parts where they can then be pipelined together to achieve the desired output.

To pipeline generators, the output of one generator function can be the input of another generator function. That resulting generator can then be used as input for another generator function, and so on.

Pipeline generators are also often referred to as nested generators. We can use a pipelined generator like in the following example:

def number_generator(): i = 0 while True: yield i i += 1 def even_number_generator(numbers): for n in numbers: if n % 2 == 0: yield n even_numbers = even_number_generator(number_generator()) for e in even_numbers: print(e) if e == 100: break

The above example contains:

  • The infinite generator number_generator() that yields numbers incrementing by 1
  • The infinite generator even_number_generator() which takes a generator as a parameter, iterates through that generator and only yields even numbers.
  • The even_numbers variable which holds an even_number_generator() object with number_generator() as its argument.

When we iterate over even_numbers only even numbers are output. The even_number_generator() iterates over all numbers using number_generator(). When an even number occurs, that number is returned by even_number_generator().

Let’s practice more with generator pipelines!

Instructions

1.

We have three courses:

  • Computer Science which has 5 students
  • Art which has 10 students
  • Business which has 15 students

First, complete the generator function called course_generator that can yield tuples of (Course name, Number students) for the above courses and the corresponding number of students. The first tuple for Computer Science has been provided.

2.

We need to add 5 students to each course. Create a generator function called add_five_students that takes in an input variable called courses. This courses object contains tuples of (Course name, Number of students). The add_five_students generator function should loop through the courses input object.

On each iteration, it should yield a tuple containing the course name and number of students plus 5. The resulting generator that is yielded should have the following values:

  • Computer Science with 10 students
  • Art with 15 students
  • Business with 20 students.
3.

Use a pipeline generator (nested generator) to get the resulting generator that has the 5 added students to each course. Set it to a variable called increased_courses.

Print out each course tuple in the resulting increased_courses generator using a for loop.

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