R1703:The if statement can be replaced with 'return bool(test)'

Question

I write a function to check if the file exists, but pylint throws a message:"R1703:The if statement can be replaced with 'return bool(test)". What the message means? In addition, how to write a pytest script to test my code below?

def is_file_valid(file):
    """
    check if input file exits
    :param file: file
    :return: True/False
    """
    if os.path.exists(file):
        return True
    else:
        return False

I've tried if ...==1: but it seems not work.

def is_file_valid(file):
    """
    check if input file exits
    :param file: file
    :return: True/False
    """
    if os.path.exists(file)==1:
        return True
    else:
        return False

For pytest script, I write...

file_test = 'test.txt'  # actually this file does not exist.
def test_is_file_valid(file_test):
    # test is_file_valid()
    assert os.path.exists(file_test) is False, "No this file"
    os.remove(file_test)

pytest only shows the following message:

ERROR test/unit/test_io_utils.py::test_is_file_valid

Do you guys have any ideas how to figure it out?

Answer 1

The suggestion means that your function could be rewritten to return a boolean result without the need for an if statement. In your case os.path.exists already returns a boolean so it's as simple as returning its result directly.

def is_file_valid(file):
    """
    check if input file exits
    :param file: file
    :return: True/False
    """
    return os.path.exists(file)

However, whether the function in this state actually makes sense, is in my opinion questionable because I don't see any "added value" compared to using os.path.exists(file) directly.

As for how to test it... create (or not) a file in Pytest's temporary folder:

def test_is_file_valid_true(tmp_path):
    file = tmp_path / 'file.txt'
    file.touch()

    assert is_file_valid(file)

def test_is_file_valid_false(tmp_path):
    file = tmp_path / 'file.txt'

    assert not is_file_valid(file)