How Do You Troubleshoot the boto Message “NoRegionError”?

Problem scenarios (one or both of the following are happening)
#1 You are getting "botocore.exceptions.NoRegionError: You must specify a region" when you run a Python program (that involves boto and AWS).

#2 You are trying to create a session with a Python/boto program. You are printing out the Session information in your Python program using boto but you see this:

Session(region_name=None)

What should you do?

Possible Solution #1
If the AWS CLI has been installed, do the following as the user who tried to run the program that caused this problem:

cd ~
ls -lhd .aws

How are the permissions set? If you see drw-------, then the error can happen. Those settings will cause the problem. To fix the problem you may need to run this: chmod u+x .aws

A less secure alternative solution would be to run this command: sudo chmod 755 .aws

Possible Solution #2
A pragmatic solution is to install and configure the AWS CLI. Once that is working, the problem should not happen. If you are using pip, see these instructions to install the AWS CLI. Otherwise see these instructions to install the AWS CLI. You may want to try to reinstall or reconfigure the AWS CLI.

Possible Solution #3
Examine the .aws/config file. Run these commands:

cd ~
cd .aws
cat config

If there is no "region =" stanza, that can cause the "NoRegionError" problem. Here is an example of a correctly configured config file:

[default]
region = us-east-2

Possible Solution #4
Are the credentials to interact with your AWS instance correct? Your Python program may use an IAM user that you do not realize it is using. Or those credentials are insufficient. Do the credentials have the ability to fetch the region you assigned?

You can test what the variable region_name is being assigned to. It is possible the logic is not assigning it to a value when the Session function is invoked.

Once the AWS CLI has been installed and configured, your Python program should recognize the region in the session. Here is a Python 3 program that can determine the AWS IAM user context your boto program would run as:

import subprocess
subprocess.run(["aws", "sts", "get-caller-identity"])