Classes and objects

Objects are refered to a container that have functions and variables coming from classes.

Classes are templates to create the object

• you have to define a variable that holds an object of the class, as follows: ` myobjectx = MyClass() `

• To access the variable inside of the newly created object: ` print(myobjectx.variable) `

Each object you create in the class will have its own versions/copies of variables and functions.

__init__ : it is a function that is called when the class is being initiated, It’s used for asigning values in a class

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Thinking Recursively in Python

What is Recursive?

The basic idea around Recursive is breaking problems into subproblems.

Recursive function is a function that calls itself until it reaches the base case (a certain condition), then it returns the result.

All recursive functions has two parts:

• base case
• recursive call

Recursive functions add to the Stack each time it is called, and once it reaches the base case it starts to return each call until excecution.

To maintain state during recursion you have to either:

• Thread the state through each recursive call so that the current state is part of the current call’s execution context
• Keep the state in global scope ¹

This is an example of a recursive function for summing numbers

Recursive data structres in Python

Any data structure that is defined by calling itself is a recursive data structure:

• Lists
• Sets
• dictionaries
• trees

and more

Naive Recursion is Naive

interesting note: Fibonacci was defined to find the number of rabbits as: ²

the number of pairs of rabbits born in a given year is equal to the number of pairs of rabbits born in each of the two previous years, starting from one pair of rabbits in the first year.

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Pytest Fixtures and Coverage

Pytest is a library in Python used to test codes

Fixtures

A fixture provides a defined, reliable and consistent context for the tests.

We can tell pytest that a particular function is a fixture by decorating it with @pytest.fixture

“parametrized tests”³

When you’re writing tests, you’re rarely going to write just one or two. Rather, you’re going to write an entire “test suite”, with each test aiming to check a different path through your code. In many cases, this means you’ll have a few tests with similar characteristics, something that pytest handles with “parametrized tests”.

• Fixtures can act like data, it executes every time you invoke a test using that fixture.
• It can make calculations and decisions.
• You can decide how often a fixture is run.

• if you set the scope of the fixture to be “module”, it’ll be available throughout your tests but will execute only a single time.³ @pytest.fixture(scope='module')

Coverage

A library that checka that your tests have run all of the code.

package: pytest-cov.

• invoke pytest with the –cov option.
• This will give you coverage of every part of your python library, so provide an argument with the option.

• You’ll need to turn the coverage report into something human-readable like HTML coverage html this will create a directory name htmlcov.

• And, you should indicate the directory into which the report should be written.
• in the index.html file, you’ll get a web-based report showing (in red) where your program still lacks coverage, add a test to cover your code.

More

1. https://realpython.com/python-thinking-recursively/ ↩

2. https://realpython.com/python-thinking-recursively/ ↩

3. https://www.linuxjournal.com/content/python-testing-pytest-fixtures-and-coverage ↩ ↩²