Sample Jenkinsfile for python3

Jenkinsfile

pipeline {
    agent {
      docker {
        image 'python:3-alpine' 
      }
    }
    stages {
        stage('build') {
          steps {
              echo 'build....'
          }
        }
        stage('test') {
          steps {
              echo 'test...'
          }
        }
        stage('for the PR') {
            when {
              branch 'PR-*'
            }
            steps {
              echo 'this only runs for the PRs'
              sh "python --version"
              sh "pwd"
              sh "ls -l"
              sh "cat manage.py"
            }
        }
    }
}