Python - 使用元组返回多个值（AWS lambda 函数）

Question

This is the current code that I have:

def handler():
    ec2 = boto3.resource("ec2", region_name="ap-southeast-2")
    instances = ec2.instances.filter(Filters=[{'Name':'iam-instance-profile.arn', 'Values': ['arn:aws:iam::123456789012:instance-profile/TestRole']}])
    for instance in instances:
        return (instance.private_ip_address)

I'm trying to return all the private_ip_addresses. This code only returns me 1 ip address but I should be getting back 3 addresses. If i did a print instead, it returns the correct 3 values

I did some research and found using tuple is a good way but it hasn't been working for me thus far. Here is an example code I'm trying out with tuple (that should work with my code if it is correct)

myList=[1,2,3,4,5,6]

def handler():
   tup=()
   for element in myList:
       tup+= (element,)
   return tup

This currently returns a null value. However, if i do print tup , it returns me with (1, 2, 3, 4, 5, 6)

Can anyone let me know where I am going wrong with my use of tuple. OR if there is a better way to do this (corresponding with how lambda functions work)?

Answer 1

The statement " return (instance.private_ip_address) " returns a tuple consisting of a single value. The fact that it is called from a loop, doesn't make any difference - as soon as the return statement is executed during the first iteration, the loop terminates.

The following should work:

def handler():
    ec2 = boto3.resource("ec2", region_name="ap-southeast-2")
    instances = ec2.instances.filter(Filters=[{'Name':'iam-instance-profile.arn', 'Values': ['arn:aws:iam::123456789012:instance-profile/TestRole']}])
    return tuple([instance.private_ip_address for instance in instances])

Answer 2

In your handler code, when you use a print instead of a return it works fine as it doesn't break the loop or the function. But when Python encounters a return, it returns the value that we've asked it to return and concludes that the function end has been reached. It doesn't continue the loop and return a value again and again.

In order to correct your code, use any data structure in python that could hold multiple values such as a tuple or a list and append any value you need to return to that within the loop and once the loop is complete, return the data structure.