仅使用Pymongo从MongoDB找到特定键

Question

我已经编写了此代码，只想检查一个名为 virtual_machines 的键。我有以下形式的数据。我只想检查 virtual_machines 是否在那里，请不要再次上传数据。

  {
          "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，但是它将输出作为无。

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 。您正在遇到错误，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

If you want to check that a key exists or not ，无论其价值如何，都使用 $存在运算符。

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