How to set default values in list of dictionary python?

Question

I have a list of dictionary accepting the user Input values as shown below:

def get_params(app_name):
    return [
           {'Key':'Path', 'Value': event['Path']},
           {'Key':'TargetType', 'Value': event['Target']},
           {'Key': 'Owner', 'Value': event['Owner']}
          ]

def lambda_handler(event,context):
     params = get_params('hello')
     print(params)

How to set default values for Path as / and TargetType as Truefor example, so that if user has not passed any value, it picks the default value?

Edit: Wanted to have default value set for Path, in case the value of event['Path'] is not found or is null.

What is a "lambda event"? All I see is a function? Are you using some framework? — cs95, Jan 19 '19 at 21:10
Sorry for using the term lambda event. Edited the question. Basically wanted to set default values in `get_params` function for all the keys. — rsram312, Jan 19 '19 at 21:18
From the parameters, I assume this is an AWS lambda function, which has nothing to do with a python lambda; I've updated the tag. — Daniel Roseman, Jan 19 '19 at 21:19
@DanielRoseman Thanks for that. Ya I was intending to add aws-lambda as a tag. — rsram312, Jan 19 '19 at 21:28
This actually has nothing to do with AWS Lambda, aside from the fact that AWS Lambda calls the `lambda_handler()` event. After that, it is all standard Python. — John Rotenstein, Jan 19 '19 at 22:03
Yeah ! Hence added that as edit , basically wanted to know how to set default values in list of dictionary . If it was just a dictionary, could have used ‘get’ and set default value . Now was wondering how to do in case of list of dictionary. — rsram312, Jan 19 '19 at 22:05
Possible duplicate of [Python: default dict keys to avoid KeyError](https://stackoverflow.com/questions/24814024/python-default-dict-keys-to-avoid-keyerror) — Uri Goren, Jan 19 '19 at 22:14

score 2 · Answer 1 · answered Jan 19 '19 at 22:12

2

A python dict has two ways of addressing its values:

events["path"] - would raise an exception if "path" not in events
events.get("path", "default") - would return "default" if the key is missing

answered Jan 19 '19 at 22:12

Uri Goren

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Thanks Uri ! This was what i was looking for. Probably, the way I put the question forward was confusing. – rsram312 Jan 19 '19 at 22:19

score 1 · Accepted Answer · answered Jan 19 '19 at 22:09

1

It appears that your requirements are:

get_params() should return values from event[]
Substitute default values if the values are not provided

You could use:

def get_params(app_name):
    return [
           {'Key':'Path', 'Value': event.get('Path', '/')},
           {'Key':'TargetType', 'Value': event.get('Target', True)},
           {'Key': 'Owner', 'Value': event['Owner']}
          ]

answered Jan 19 '19 at 22:09

John Rotenstein

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Thanks a lot John !! This is what I was looking for. I was trying to use `get` , but had got the syntax wrong inside a list of dictionary. Thanks again, this worked perfectly :+1: – rsram312 Jan 19 '19 at 22:17

How to set default values in list of dictionary python?

2 Answers2