A quick example for using roles within a boto3 script

boto3_sts_assumerole

import boto3
 
acct1_arn = 'arn:aws:iam::111111111111:role/S3-Write-Role'
acct2_arn = 'arn:aws:iam::222222222222:role/S3-Read-Role'
 
def switch_role(role_arn):
    sts_client = boto3.client('sts')
    response = sts_client.assume_role(
        RoleArn=role_arn,
        RoleSessionName="AssumeRoleSession"
    )
    session = boto3.Session(
        aws_access_key_id=response['Credentials']['AccessKeyId'],
        aws_secret_access_key=response['Credentials']['SecretAccessKey'],
        aws_session_token=response['Credentials']['SessionToken']
    )
    return session
 
 
def acct1_function():
    session = switch_role(role_arn=acct1_arn)
    s3 = session.client('s3')
    # Do some S3 stuff in acct1
 
def acct2 function():
    session = switch_role(role_arn=acct2_arn)
    s3 = session.client('s3')
    # Do some S3 stuff in acct2