使用pymongo只从mongodb中找到特定的密钥

Question

我已经编写了这段代码，我只想检查一个名为Virtual_Machines的密钥。我有以下表格的数据。我只想检查一下是否有Virtual_Machines，那么就不要再上传数据了。

  {
          "Virtual_Machines": {
               "Debian": {
                    "VM_Name": "Debian",
                    "VM_Location": "eastus",
                    "VM_Disk_Name": "Debian_OsDisk_1_b890f5f5c42647549c881c0706b85201",
                    "VM_Publisher_Info": {
                         "publisher": "debian",
                         "offer": "debian-11",
                         "sku": "11-gen2",
                         "version": "latest"
                    },
                    "Vm_Disk_Type": "Standard_D2s_v3",
                    "VM_Encryption": null
               },
               "Ubuntu": {
                    "VM_Name": "Ubuntu",
                    "VM_Location": "eastus",
                    "VM_Disk_Name": "Ubuntu_disk1_0610e0fde49b481490ef0a069a03b460",
                    "VM_Publisher_Info": {
                         "publisher": "canonical",
                         "offer": "0001-com-ubuntu-server-focal",
                         "sku": "20_04-lts-gen2",
                         "version": "latest"
                    },
                    "Vm_Disk_Type": "Standard_D2s_v3",
                    "VM_Encryption": null
               }
          }
     },

我的代码是，但它以None的形式提供输出。

db = client['Audit']
vms = db['virtual_machine']
vm = json.dumps(vm)
vmachine = vms.find_one({"Virtual_Machine"},{'_id':0})    

print(vmachine)

Answer 1

find_one()中的第一个参数必须是dict。您正在获得错误，因为您正在传递{"Virtual_Machine"}，python将其解释为set https://docs.python.org/3/library/stdtypes.html#set。

如果要检查键是否存在，无论其值如何，请使用$exists运算符。https://www.mongodb.com/docs/manual/reference/operator/query/exists/

vms.find_one({'Virtual_Machines': {'$exists': True}}, {'_id':0})