Tried this:
import boto3
from boto3.s3.transfer import TransferConfig, S3Transfer
path = \"/temp/\"
fileName = \"bigFile.gz\" # this happens to be a 5.9 Gig
In your code snippet, clearly should be part -> part1 in the dictionary. Typically, you would have several parts (otherwise why use multi-part upload), and the 'Parts' list would contain an element for each part.
You may also be interested in the new pythonic interface to dealing with S3: http://s3fs.readthedocs.org/en/latest/