pydantic：在班级的所有实例中进行迭代

Question

我想迭代Pydantic的所有类（服务器）的现有实例：

from datetime import datetime
from typing import List, Optional
from pydantic import BaseModel
from pydantic.schema import schema

class Share(BaseModel):
    exportstring: str
    mountpoint: str
    options: str

class Server(BaseModel):
    srvname: str
    shares: List[Share]

class ServerList(BaseModel):
    __root__: List[Server]

    def __iter__(self):
        return iter(self.__root__)

    def __getitem__(self, Server):
        return self.__root__[Server]

srv1 = Server(srvname="horst1", shares=[Share(exportstring='export1server:/vol/asdfasdf', mountpoint='/opt/bla', options='nfsvers=4,rw,sync'), Share(exportstring='export1server:/vol/blub', mountpoint='/opt/bluba', options='nfsvers=4,rw,sync')])

srv1 = Server(srvname="harry", shares=[Share(exportstring='export1server:/vol/asdfasdf', mountpoint='/opt/bla', options='nfsvers=4,rw,sync'), Share(exportstring='export1server:/vol/blub', mountpoint='/opt/bluba', options='nfsvers=4,rw,sync')])

我试图使用这种Metaclass ServerListe，但没有成功……

类似这样的事情是行不通的：

for item in ServerList:
    print(item)

有什么想法吗？

Answer 1

您可以通过编写自己的__ Init __来做到这一点，调用超级__ init __ init __将实例注册到某些注册表（此处的列表），然后迭代注册表。

技巧不在__ Init __管道中。诀窍是Pydantic class创建机制（赌某个地方的Metaclass）删除了它不像Bona实例级别的Pydantic领域。因此，我不得不将server_list放在班级外。

from datetime import datetime
from typing import List, Optional, Any
from pydantic import BaseModel
from pydantic.schema import schema



class Share(BaseModel):
    exportstring: str
    mountpoint: str
    options: str


class Server(BaseModel):
    srvname: str
    shares: List[Share]

    #this doesn't worker.  The actual server class only gets declared
    #pydantics fields and pydantic utility methods/variables.
    #list : Any = []

    def __init__(self, *args, **kwargs):
        super(Server,self).__init__(*args,**kwargs)
        server_list.append(self)

#have to declare standalone variable, or at least one outside
#of pydantic class definitions
server_list = []


srv1 = Server(srvname="horst1", shares=[Share(exportstring='export1server:/vol/asdfasdf', mountpoint='/opt/bla', options='nfsvers=4,rw,sync'), Share(exportstring='export1server:/vol/blub', mountpoint='/opt/bluba', options='nfsvers=4,rw,sync')])
srv2 = Server(srvname="harry", shares=[Share(exportstring='export1server:/vol/asdfasdf', mountpoint='/opt/bla', options='nfsvers=4,rw,sync'), Share(exportstring='export1server:/vol/blub', mountpoint='/opt/bluba', options='nfsvers=4,rw,sync')])

#hardcoded iteration
for srv in [srv1,srv2]:
    print(f"\n\n{srv=}")

# for srv2 in Server.list:

#registered by class 
for srv2 in server_list:
    print(f"\n\n{srv2=}")

输出：

srv=Server(srvname='horst1', shares=[Share(exportstring='export1server:/vol/asdfasdf', mountpoint='/opt/bla', options='nfsvers=4,rw,sync'), Share(exportstring='export1server:/vol/blub', mountpoint='/opt/bluba', options='nfsvers=4,rw,sync')])


srv=Server(srvname='harry', shares=[Share(exportstring='export1server:/vol/asdfasdf', mountpoint='/opt/bla', options='nfsvers=4,rw,sync'), Share(exportstring='export1server:/vol/blub', mountpoint='/opt/bluba', options='nfsvers=4,rw,sync')])


srv2=Server(srvname='horst1', shares=[Share(exportstring='export1server:/vol/asdfasdf', mountpoint='/opt/bla', options='nfsvers=4,rw,sync'), Share(exportstring='export1server:/vol/blub', mountpoint='/opt/bluba', options='nfsvers=4,rw,sync')])


srv2=Server(srvname='harry', shares=[Share(exportstring='export1server:/vol/asdfasdf', mountpoint='/opt/bla', options='nfsvers=4,rw,sync'), Share(exportstring='export1server:/vol/blub', mountpoint='/opt/bluba', options='nfsvers=4,rw,sync')])