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Mastering the Art of Programming in Python 3

Solution: Task V to Task VIII

Explore how to implement matrix addition, multiplication, and scalar intensification using coroutines in Python. Understand managing matrix operations in series, switching between operations with nested generators, and handling exceptions. This lesson reinforces Python coroutine patterns for advanced matrix manipulations.

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Explanation

Task 5: Add matrices in series

You were to add matrices in the order the coroutine add_series receives them.

Look at the following code.

Python 3.10.4
from matrix import Matrix
import contextlib
from functools import wraps
# Generator function decorated
@contextlib.contextmanager
def readFile(filename, mode):
    myfile = open(filename, mode) # Executed before the block
    yield myfile
    
    myfile.close()                # Executed after the block
# Reading matrix from file
def read_matrix(filename):
    matrix = []
    with readFile(filename, 'r') as fp:
        for line in fp:
            matrix.append([int(num) for num in line.split()]) 
    return matrix
# Reading matrices
matrix1 = Matrix(read_matrix('matrix1.txt'))
matrix2 = Matrix(read_matrix('matrix2.txt'))
# Priming a coroutine
def coroutine(func):
  @wraps(func)
  def primer(*args, **kwargs):
    generator = func(*args, **kwargs)
    next(generator)
    return generator
  return primer
# Adding matrices in series
@coroutine
def add_series():
    result = Matrix(None)
    while True:
        curr_matrix = yield result
        if result.matrix is None:   # First retrieval
            result.matrix = curr_matrix.matrix  
            result.print()
        else:
            try:
                result = curr_matrix + result   # Adding previous result
            except:
                print('Cannot add.')
            else:
                result.print()
cr = add_series()
cr.send(matrix1)
cr.send(matrix2)
m = Matrix([[0,0]])
cr.send(m)
cr.send(matrix1)
cr.close()

In main, look at the header of add_series at line 39. We create a matrix result. It’s empty, initially. Look at line 43. We apply this condition because we want the process to continue until a user is sending some values. We are yielding result as this value, which will possibly change in every step. When a user sends a value, it will be stored in curr_matrix.

Now, at the time when add_series gets a value for the first time, the result would be None. So, its value needs to be updated as curr_matrix (see line 47). There has to be no addition at the first step, as per the requirement.

After the first step, whenever the user sends a value again, ...