以下是一个使用Python SDK从GCP中的定期快照中恢复实例的示例代码：

import googleapiclient.discovery
import google.auth

# 获取GCP凭证
credentials, project = google.auth.default()

# 创建Compute Engine的服务对象
compute = googleapiclient.discovery.build('compute', 'v1', credentials=credentials)

# 定义要恢复的实例和快照的信息
zone = 'us-central1-a'
instance_name = 'my-instance'
snapshot_name = 'my-snapshot'

# 获取快照的最新状态
snapshot_response = compute.snapshots().get(project=project, snapshot=snapshot_name).execute()
snapshot_status = snapshot_response['status']

# 如果快照状态为READY，则创建一个新的实例，并使用快照进行恢复
if snapshot_status == 'READY':
    source_disk = snapshot_response['sourceDisk']
    source_disk_id = source_disk.split('/')[-1]

    source_disk_body = {
        'sourceDisk': f'projects/{project}/zones/{zone}/disks/{source_disk_id}'
    }

    # 创建新实例的配置
    new_instance_body = {
        'name': instance_name,
        'machineType': f'projects/{project}/zones/{zone}/machineTypes/n1-standard-1',
        'disks': [source_disk_body],
        'networkInterfaces': [{
            'network': 'global/networks/default',
            'accessConfigs': [{
                'type': 'ONE_TO_ONE_NAT',
                'name': 'External NAT'
            }]
        }]
    }

    # 创建新实例
    operation = compute.instances().insert(project=project, zone=zone, body=new_instance_body).execute()
    print(f"Instance '{instance_name}' is being created. Operation ID: {operation['name']}")
else:
    print(f"Snapshot '{snapshot_name}' is not ready, current status: {snapshot_status}")

请确保已安装并正确设置了Google Cloud SDK，并且已使用gcloud auth application-default login命令进行了身份验证。