AWS Lambda Python 3 检查事件变量是否存在

Question

 try: 
        event['ids']
 except NameError: 
        ids = None

This is throwing a KeyError. I just want to check if the event variable exists and set to none or pass the value if it does. I have also tried to use

if (len(event['ids']) < 1) 

but get an error. Am I missing something? I may or may not have all my event keys passed and want to check for existence.

Answer 1

Use the get method. The second parameter is the default value if the key doesn't exist in the dictionary. It's the standard way to get values from a dictionary when you're not sure if the key exists and you don't want an exception.

ids = event.get('ids', None)

Answer 2

We can check if the key 'key1' exists in the Json dictionary.

{ 
"key1":"value1"
}

To retrieve the value 'value1' if the key 'key1' exists in the dictionary.

if event.get('key1',None) != None:
   value = event.get('key1',None)