How to select a parameter of a class in Python?-CodePudding

everyone. I would need help to understand how to select a parameter of a class. I am studying them now and can't figure out how to select the data I need.

As you can see from the code below, I would like to get the value of Xxxx() in a3 or a4, it makes no difference, but I don't understand what should I do? How do I select it and use it in a variable or print it out?

Thanks for the help

class Xxxx_Item:
""" """
def __init__(self, name, a1, a2, a3, a4):
    self.name = name
    self.a4 = a4
    self.itemss = {
        'a1': a1,
        'a2': a2,
        'a3': a3
    }


class Xxxx:
    """ """
    def __init__(self):
        self.xxx = [
            Xxxx_Item(name="A", a1=1, a2=2, a3=3, a4=4)
        ]

base = Xxxx()

I've tried several ways but can't do it.

with print(base) returns to me:

<__main__.Xxxx object at 0x000001FAF464E560>

I try:

base.xxx[1]                  #  IndexError: list index out of range
base.xxx[Xxxx_Item[2]]       # TypeError: 'type' object is not subscriptable
base.xxx[[0][2]]             # IndexError: list index out of range

I am a bit puzzled about how the selection of a specific value within a class works.

CodePudding user response：

Xxxx_Item contains a member named name, a member named a4 and a member named itemss that holds a dictionary from string to whatever's passed in.

Xxxx contains member xxx that holds a list containing one Xxxx_Item

To access members, you have to index into them appropriately:

`a4`

print(base.xxx[0].a4)

Start with base, then access the member xxx with .xxx, then get the first item of this list with [0] (which is an Xxxx_Item), then access its a4 member with .a4

`a3`

print(base.xxx[0].itemss["a3"])

Start with base, then access the member xxx with .xxx, then get the first item of this list with [0] (which is an Xxxx_Item), then access its itemss member with .itemss (which is a dictionary), then find what's in the "a3" key with ["a3"]

Does this answer your question?

CodePudding user response：

I didnt understand why do you need second class but you can define methods to get every parameter you want in Xxxx_Item class, for example:

class Xxxx_Item:

    def __init__(self, name, a1, a2, a3, a4):
        self.name = name
        self.a4 = a4
        self.itemss = {
            'a1': a1,
            'a2': a2,
            'a3': a3
        }

    def get_name(self):
        return self.name

base = Xxxx_Item()
print(base.get_name())

If you want to use your second class you still define a method to get parameters, for example:

class Xxxx_Item:

    def __init__(self, name, a1, a2, a3, a4):
        self.name = name
        self.a4 = a4
        self.itemss = {
            'a1': a1,
            'a2': a2,
            'a3': a3
        }

    def get_name(self):
        return self.name

class Xxxx:
    
    def __init__(self):
        self.xxx = [
            Xxxx_Item(name="A", a1=1, a2=2, a3=3, a4=4)
        ]


base = Xxxx()
print(base.xxx[0].get_name())