Setup An Application Configuration File In Python

it's a common practice to store configuration variables in a configuration file and retrieve the properties while they are needed.

Python provides a module called ConfigParser to help managed application configurations. The configParser module can be used to create a configuration file as well as to retrieve property values from a configuration file.

A configuration file in Python is similar to a Windows version of init (.ini) file. The file is divided by “Sections” and “options”. Following is a sample configuration file:

[DEFAULT]
work_directory =/tmp
Log_directory = /var/logs
app_user = app

[DEVELOPMENT]
hostname = mydevhost.com
database = devdb
user_id =devuser
Password =

[STAGE]
hostname = mystagehost.com
database = stagedb
user_id =stageuser
Password =

In the above example, [DEFAULT], [DEVELOPMENT], and [STAGE] are called section. Work_directory, log_directory, hostname,etc are called option.

Here is an example of how to retrieve the properties from the configuration file assuming the above configuration filename is called config.cfg:

import configparser
class GetConfigProperty():

def get_property(self,config_file: str, section: str, property: str) -> str:
     property_value: str
     config = configparser.ConfigParser()
     config.read_file(open('./config/' + config_file))
     property_value = config.get( section, property,fallback=None)
     return property_value

Now, we can call the above function to get the configuration properties in the application like the following:

getConfigProperty = GetConfigProperty()
working_dir : str = getConfigProperty.get_property("config.cfg", "DEFAULT", "working_dir");
dev_hostname : str = getConfigProperty.get_property("file_config.cfg", "DEVELOPMENT", "hostname");

Related Post: Setup Logging In Python

Docker Command Cheat Sheet

List docker images on the host

$ docker images

List docker containers that are currently running:

$ docker ps

List Containers

$ docker container ls

Delete an image

$ docker rmi <image id>

$ docker rmi --force <image id> #force delete

Remove all images

$ docker rmi $( docker images -q)

Stop All the containers

$ docker stop $( docker ps -aq)

Remove all containers

$ docker rm $( docker ps -aq)

Log Into an Container

$ docker exec -i -t <container id> sh

Run an Docker Image

$ docker run -i -t <image id>

Docker Documents

• How To Install and Use Docker In Ubuntu

• Docker Compose

• Docker Variable Substitution

• Docker Storage

SQL Query To Select Row Number, Rank, And Dese Rank

Use Analytic Functions

SELECT e.name as emp_name, d.name dept_name, e.salary,
      ROW_NUMBER() OVER(Partition by d.name ORDER BY e.salary DESC) AS row_num 
      FROM employee e join department d on e.dept_id = d.dept_id
     
 
SELECT e.name as emp_name, d.name dept_name, e.salary,
      RANK() OVER(Partition by d.name ORDER BY e.salary DESC) AS rank
      FROM  employee e join  department d on e.dept_id = d.dept_id
     

SELECT e.name as emp_name, d.name dept_name, e.salary,
      DENSE_RANK() OVER(Partition by d.name ORDER BY e.salary DESC) AS dense_rank 
      FROM  employee e join  department d on e.dept_id = d.dept_id

Without Using Analytic Function

select emp.*,
       (select count(*)
        from employee emp2
        where emp2.dept_id = emp.dept_id  

              and(emp2.salary > emp.salary or emp2.salary = emp.salary  

                   and emp2.emp_id <= emp.emp_id
                  )
       ) as "row_number",
       (select 1 + count(*)
          from employee emp2
          where emp2.dept_id = emp.dept_id and                 emp2.salary > emp.salary 
       ) as "rank",
       (select count(distinct salary)
        from employee emp2
        where emp2.dept_id = emp.dept_id and              emp2.salary >= emp.salary
       ) as "dense_rank"
from employee emp;