A connection to the notebook server could not be established. The notebook will continue trying to reconnect, but until it does, you will NOT be able to run code. Check your network connection or notebook server configuration

This problem is due to incorrect configuration of torando server. You need to uninstall tornado version 6 and install tornado version 5.1.1

To uninstall run : pip uninstall tornado

Install tonado : pip install tornado==5.1.1

How and why use SQLite in R

If you need small amount of data to work with( like development of a alert system to store alert conditions). Using a full fleged db would be painful.

Most of Programming system have sqlite drivers inbuilt, therefore no need to install any other driver.

First you need to install R package for sqlite database

install.packages("RSQLite") 

Basic usage of RSQLite package ( code snippet)

> library(DBI) 
> con <- dbConnect(RSQLite::SQLite(), ":memory:")
> con2 <- dbConnect(RSQLite::SQLite(), "mydb.sqlite")
> dbListTables(con) #list the tables character(0)
> dbWriteTable(con, "mtcars", mtcars)
> dbListTables(con) #list the tables
> res <- dbSendQuery(con, "SELECT * FROM mtcars WHERE cyl = 4")
> dbFetch(res)
> dbClearResult(res)

R package Installation failed: Timeout was reached: Resolving timed out after 10000 milliseconds

If you are facing problems like above, timeout may be problem of your network( domain name resolution). 
Possible solution is to update the network dns . It should be fast dns like Google DNS or Cloudflare DNS 

Google DNS – 8.8.8.8,8.8.4.4
Cloudflare DNS – 1.1.1.1

With low latency network and responsive dns, this problem will be resolve as resolved in above image. 

This post is also answer to how to install IRkernal for jupyter notebook 

Flask sqlalchemy error : SQLALCHEMY_TRACK_MODIFICATIONS

Problem :FSADeprecationWarning: SQLALCHEMY_TRACK_MODIFICATIONS adds significant overhead and will be disabled by default in the future. Set it to True or False to suppress this warning.
‘SQLALCHEMY_TRACK_MODIFICATIONS adds significant overhead and ‘

Solution:  app.config[‘SQLALCHEMY_TRACK_MODIFICATIONS’] = False

Vue JS Issue – Devtool inspection is not available

Full description of problem:  Vue.js is detected on this page. Devtools inspection is not available because it’s in production mode or explicitly disabled by the author.

Cause: You may be using compressed production version of vue

Solution : You need to use development version with debugging support.
<script src=”https://vuejs.org/js/vue.js” ></script>



vue.js source

If your problem solved, share this to others. 

How to improve python requests module with retries and timeouts

I found this useful article at https://www.peterbe.com/plog/best-practice-with-retries-with-requests

Most of time, It will be useful to retry the requests so request loop could be process successfully.

While accessing any webpage, there may be different types of timeout. 


Connection timeout => Time taken to identify the resolved ip and connect to them

Read timeout => Time taken to get response from connected server. If this take longer time, then will be read timeout

connect_timeout, read_timeout = 5.0, 30.0
response = requests.get(URL, timeout=(connect_timeout, read_timeout))