使用 *args 和 **kwargs 的字典理解

Question

I'm new to Python. I have to do a little exercise. I have two classes RealNumber and ComplexNumber and I need to create a new class, with, as an attribute, a dictionary (dict_number) that contains an integer as a key and a RealNumber or ComplexNumber object as value. In the init method, with parameters *args and **kwargs, each arg in *args must be entered with an increasing integer key (using the dict comprehension) (eg {0: RealNumber0, 1: RealNumber1, 2: ComplexNumber0}) while for each arg in kwargs it will be necessary to insert the parameter name: value. Now, I have already created the classes RealNumber and ComplexNumber, but I'm having issues doing the third class. How can I create a dict that have an incremental value as key and a tuple (object name, object value) as value? The dictionary must have this form: {incremental key: (name_object, object value)} , for example: {0: Realnumber 5, 1: ComplexNumber 1+3i...} Where 0: is the incremental key; Realnumber is the name of the object class; 5 is the value contained by the Realnumber class object.

...

class NumbersCollection:  # I've issues here
     def __init__(self, *args, **kwargs):
         self.dict_numbers = {key: arg for key, arg in kwargs.items()} 

if __name__ == '__main__':
    x = RealNumber(5)
    y = ComplexNumber(1, 3) #first parameter is the real part, the 2nd is the imaginary part

    print(f"Number: {x.number}")
    print(f"RealPart: {y.numPart}, ImPart: {y.imPart}")

    d = NumbersCollection(a=x, b=y) # I've issues here

...

Answer 1

How about this?

class NumbersCollection:
    def __init__(self, **kwargs):
        self.dict_numbers = {
            i: (key, value) for i, (key, value) in enumerate(kwargs.items())
        }

>>> nums = NumbersCollection(a=1, b=2)
>>> nums.dict_numbers
{0: ('a', 1), 1: ('b', 2)}

Answer 2

To be honest, you are asking too many questions in a single question. So there is another answer.

__repr__

You can modify representation of an object of a class defining __repr__ method on a class:

class SomeClass:
    def __init__(self, value: int) -> None:
        self.value = value

    def __repr__(self):
        return f"SomeClass {self.value}"

>>> SomeClass(1)
SomeClass 1

enumerate

You can use enumerate function on an iterable to iterate objects in a sequence, returning index as first value and value of an object as second value

data = {
    "a": 1,
    "b": 2,
    "c": 3,
}

>>> for i, (key, value) in enumerate(data.items()):
...     print(i, key, value)
...
0 a 1
1 b 2
2 c 3

Answering your question,

combine this techniques to get the desired answer.

Using __repr__ :

class RealNumber:
    def __init__(self, value: int) -> None:
        self.value = value

    def __repr__(self):
        return f"RealNumber {self.value}"


class ComplexNumber:
    def __init__(self, value: int, imaginary_part: int) -> None:
        self.real_part = value
        self.imaginary_part = imaginary_part

    def __repr__(self):
        return f"ComplexNumber {self.real_part}+{self.imaginary_part}i"

Using enumerate :

class NumbersCollection:
    def __init__(self, *args: Union[RealNumber, ComplexNumber]):
        self.dict_numbers = dict(enumerate(args))

The use of dictionary comprehension there is not required as dict(enumerate(args)) does the same, but better and cleaner. You can, of course, use them if it is a requirement of your assignment.

class NumbersCollection:
    def __init__(self, *args: Union[RealNumber, ComplexNumber]):
        self.dict_numbers = {i: value for i, value in enumerate(args)}

Both should produce the same answer.

>>> nums = NumbersCollection(RealNumber(1), ComplexNumber(1, 2))
>>> nums.dict_numbers
{0: RealNumber 1, 1: ComplexNumber 1+2i}