delete a Python object that matches an atribute

[Gribouillis]

The problem is that you are trying to use the garbage collector as a container for the tech_dispo instances. That's not the way it should be used. In normal code, one does not interact directly with the garbage collector. When you need a container for a collection of instances, just create one. See the below example: I create a class TechDispoTeam, which is just a kind of dictionary to keep the instances. Potentially, I could have several teams

class TechDispo:
    
    def __init__(self, nom, ip, pc):
        self.nom = nom
        self.ip = ip
        self.pc = pc

    def __repr__(self):
        return "TechDispo{}".format((self.nom, self.ip, self.pc))
        
class TechDispoTeam(dict):
    def tech_dispo(self, nom, ip, pc):
        if nom not in self:
            self[nom] = TechDispo(nom, ip, pc)
        return self[nom]

team = TechDispoTeam()

t1 = team.tech_dispo('carl', '10.192.168.1', 'PC-01')
t2 = team.tech_dispo('Stéphane', '10.192.168.2', 'PC-02')

print('There are {} techs in the team'.format(len(team)))

# show all instances
for t in team.values():
    print(t)
    
# delete instance with ip '10.192.168.1'
for nom, t in list(team.items()):
    if t.ip == '10.192.168.1':
        del team[nom]

print('There are {} techs in the team'.format(len(team)))

Several questions could be addressed: what to do if the team recruits a second Carl? What to do if we call team.tech_dispo('carl', '10.192.168.7', 'PC-5') but Carl is already in the team? Should the new IP and PC replace the old ones for Carl? The current code ignores the new settings, etc.