How to make sure that no other instances have the same name from a class

Question

class Satellite:
  
  def __init__(self, message):
    print(message)
    self.name = input("name: ").title()
    self.lbs = int(input("lbs: "))
    self.speed = int(input("speed: "))

lstSat = []
e= input("Would you like to create satellites? If yes, type O. If not, type another letter: ").lower()
i=0
while e=="o":
    lstSat.append(Satellite("Info for satellite "+str(i+1)))
    i+=1
    e= input("Type O to create another satellite: ").lower()

Hello,

How can I make sure that 2 Satellites cannot be the same?

What do you want to happen if the same name is entered? Should it raise an exception? Silently overwrite the existing satellite of the same name? — Samwise, Dec 07 '22 at 19:32
Does [this answer](https://stackoverflow.com/q/12101958/4583620) help? — Michael Ruth, Dec 07 '22 at 19:50

DarkKnight · Answer 1 · 2022-12-07T19:55:14.743

Please don't ask for user input during class construction. Much better to acquire the values elsewhere then use a straightforward constructor based on the user's input values.

In order to determine repetition, you need to override the eq dunder method.

Try this:

class Satellite:
    def __init__(self, name, lbs, speed):
        self._name = name
        self._lbs = lbs
        self._speed = speed
    def __eq__(self, other):
        if isinstance(other, str):
            return self._name == name
        if isinstance(other, type(self)):
            return self._name == other._name
        return False
    def __str__(self):
        return f'Name={self._name}, lbs={self._lbs} speed={self._speed}'

lstSat = []

PROMPT = 'Would you like to create satellites? If yes, type O. If not, type another letter: '

while input(PROMPT) in 'Oo':
    name = input('Name: ').title()
    if name in lstSat:
        print(f'{name} already in use')
    else:
        lbs = int(input('lbs: '))
        speed = int(input('Speed: '))
        lstSat.append(Satellite(name, lbs, speed))

for satellite in lstSat:
    print(satellite)

score 1 · Accepted Answer · answered Dec 07 '22 at 19:40

I would go for iteration in list and check names with every satellite

...
while e=="o":
    satellite = Satellite("Info for satellite " + str(i+1))
    if check_reapeated_name(lstSat, satellite.name): # see definition of function bellow
        lstSat.append(satellite)
    else:
        # here do some output or error handling
    ...
...

and the definition of check_reapeated_name() would be something like this:

def check_reapeated_name(lstSat, satellite_name):
    for i in lstSat:
        if i.name == satellite_name:
             return False
    return True

How to make sure that no other instances have the same name from a class

2 Answers2