how do i print an array of custom objects in python?

Question

im a networking guy trying to learn some python to be able to automate. im having a difficult time grasping OOP. wrote the script below (not perfect i would assume) to experiment, and i keep getting the following as output:

main.Router object at 0x0000021C68033E80

my script:

class Router:
    name=''
    def __init__(self,ip,network):
        self.ip = ip
        self.network=network

    def getip(self):
        print(self.ip)
    def getname(self):
        print(self.name)
    def getnetwork(self):
        print(self.network)

class Switch(Router):
    def __init__(self,ip,network,layer):
        Router.__init__(self,ip,network)
        self.layer=layer
        self.vlans=[]
    def addvlan(self,vlan):
        self.vlans.append(vlan)
    def getvlans(self):
        print(self.vlans)
    def getlayer(self):
        print(self.layer)

routers=[]
switches=[]
while(True):
    rors = ""
    while(rors != "router" and rors!= "switch" and rors != "0"):
        rors = input("router or switch? 0 to exit: ")
    if(rors=="router"):
        routers.append(Router(input("enter ip: "),input("enter network: ")))
    elif(rors=="switch"):
        switches.append(Switch(input("enter ip: "),input("enter network: "),input("layer?: ")))
        stop=1
        while(stop!=0):
            stop=int(input("enter 1 to continue, 0 to stop adding vlans: "))
            if(stop==0):break
            switches[len(switches)-1].addvlan(int(input("add vlan: ")))
    elif(rors == "0"):
        break
    else: print("input error")

print(switches)
print(routers)

i understand that by printing the lists i just print where the memory pointer is pointing, but how do i make it so the values themselves are the ones actually being printed? thanks for the help!

you probably want to override either the __str__ or __repr__ method — dangee1705
– dangee1705, Commented Jan 23, 2021 at 23:59
@dangee1705: Given they're printing lists of the objects, definitely __repr__; list always prints the repr of the contained objects. — ShadowRanger
– ShadowRanger, Commented Jan 24, 2021 at 0:02
@ShadowRanger yeah that sounds about right, I can never remember the difference between the two — dangee1705
– dangee1705, Commented Jan 24, 2021 at 0:08

Czaporka · Accepted Answer · 2021-01-24 02:30:47Z

2

You need to override the __repr__ method to change the string representation of the objects. Here's an example:

In [1]: class A1:
   ...:     def __init__(self, a, b):
   ...:         self.a = a
   ...:         self.b = b
   ...:

In [2]: class A2:
   ...:     def __init__(self, a, b):
   ...:         self.a = a
   ...:         self.b = b
   ...:     def __repr__(self):
   ...:         kvps = [f"{k}={v}" for k, v in vars(self).items()]
   ...:         return f"{type(self).__name__}({', '.join(kvps)})"
   ...:

In [3]: A1(1, 2)
Out[3]: <__main__.A1 at 0x7f533357fe20>

In [4]: A2(1, 2)
Out[4]: A2(a=1, b=2)

answered Jan 24, 2021 at 2:30

Czaporka

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