def is_number(s):
    """Check if `s` is a number.

    Parameters
    ----------
    s : str, int, float, list
        Variable for which the function checks, if it is a number.

    Returns
    -------
    bool
        True, if the variable is a number. For example 1, 1.0.
        False, if the variable is not a pure number. For example "a", "1a".

    """
    try:
        float(s)
        return True
    except ValueError:
        return False