AWS Python Lambda with multiple functions

Question

I have an AWS Lambda function in python3.7. The way its set up im running the lambda_handler(event, context) function and passing data to a separate function that calls itself multiple times depending on what is passed into it. How do I then return data from the second function?

import json
import boto3

def lambda_handler(event, context):
    # code to get initial data
    x = second_function(data)
    print(x)
    return x



def second_function(data):
    # code to manipulate data
    if condition:
       print(newData)
       second_function(newData)
    else:
       return allData

I expected this to return allData back through the lambda_handler function, but instead returns null

And logged is

newData
newData
newData
None

I am using the second function to get data based on the last PaginationToken. Is there a better way to get paginated data rather than creating a second recursive function?

Your second_function() doesn't seem to return anything if condition is true. And if condition is false, it appears that allData is empty (None). — John Rotenstein
– John Rotenstein, Commented Feb 11, 2019 at 0:49
if condition is true the second_function calls itself and sends what it has already gotten. If the condition is false (when it reaches the final page) it is supposed to return all the data combined — bjwhip
– bjwhip, Commented Feb 11, 2019 at 1:07

John Rotenstein · Accepted Answer · 2019-02-11 00:47:29Z

1

One option is to use a boto3 paginator.

Alternatively, you could use a loop rather than a recursive function.

It would be something like:

response = api_call()
<do stuff with response>
while response['NextToken']:
    response=api_call(NextToken=response['NextToken'])
    <do stuff with response>

You can probably avoid having to double-up the <do stuff> bit by improving on the while statement.

answered Feb 11, 2019 at 0:47

John Rotenstein

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1 Comment

bjwhip Over a year ago

Thanks! I'm fairly new to python and didn't think to use a while statement

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