How to use awscli inside python script?

You can do it with brilliant sh package. You could mimic python package with sh doing wrapping for you.

import sh
s3 = sh.bash.bake("aws s3")
s3.put("file","s3n://bucket/file")

Boto3 doesn't have everything the cli has so you may have to use something from the cli in a script once in a blue moon. I can't find an analog for aws deploy push in boto3 for example so here is how I push to s3 with the cli from a python script. Although to Julio's point, I use boto for everything else.

import subprocess

cmd='aws deploy push --application-name SomeApp --s3-location  s3://bucket/Deploy/db_schema.zip --ignore-hidden-files' 
push=subprocess.Popen(cmd, shell=True, stdout = subprocess.PIPE)
print push.returncode

The CLI would be more suited for the shell prompt, for a better python API, check the boto library. This example shows how to launch an instance: http://boto.readthedocs.org/en/latest/ec2_tut.html