Besides using cfn-lint through the command line, cfn-lint is built as a standalone Python module, allowing it to be integrated in your own (existing) codebase. In this way you can extend your own toolkit or CI/CD solution with cfn-lint feedback.
A simplified api is exposed by cfnlint.api which allows you to validate string CloudFormation templates on the fly.
We can use either lint(s, config) which validates a string s against the specified config, or we can use lint_all(s) which simply validates s against all rules and regions:
from cfnlint.api import lint, lint_all, ManualArgs
# Note ServiceName is not defined anywhere here
s = '''AWSTemplateFormatVersion: 2010-09-09
Description: An example CloudFormation template for Fargate.
Resources:
Cluster:
Type: AWS::ECS::Cluster
Properties:
ClusterName: !Join ['', [!Ref ServiceName, Cluster]]'''
config = ManualArgs(regions=["us-east-1"])
print(lint(s, config=config))
# [[E1012: Check if Refs exist] (Ref ServiceName not found as a resource or parameter) matched 7]
print(lint_all(s))
# [[I1022: Use Sub instead of Join] (Prefer using Fn::Sub over Fn::Join with an empty delimiter) matched 7, [E1012: Check if Refs exist] (Ref ServiceName not found as a resource or parameter) matched 7]