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Connecting Oracle with Python via cx_Oracle extension

Installation Prerequisites

• Python 2.7, 3.5 or above
• Oracle Client / Oracle Instant Client "Basic" or "Basic Light"
• libaio / libaio1 package

Installation Reference

• cx_Oracle
• Installation guide

Sample Python Code

import cx_Oracle

# Make DSN address. Real values for host address, port and service name were replaced by '<>'.
dsn = cx_Oracle.makedsn('<host_address>', '<port>', service_name='<service_name>')

# Connect to DSN
orcl = cx_Oracle.connect(user='<username>', password='<password>', dsn=dsn)

# Get cursor
cursor = orcl.cursor()

# Execute SQL statement
cursor.execute('<SQL SELECT STATEMENT>')

# Fetch result
data = cursor.fetchone()

Sending F10 in Ubuntu Terminal

By default, you just can't send F10 to Ubuntu Terminal's curses program. This is because F10 is being captured by Terminal.app already.

A quick workaround is to use "ESC 0" to simulate sending F10 inside Terminal.app.

Reference

Customized Dash (Launcher / Taskbar) Icon in Ubuntu

To customize application icon in Ubuntu:

1. Create a .desktop file in ~/.local/share/applications/
   e.g. /home/user/share/applications/<application name>.desktop
   
2. Add the following content to the desktop file

[Desktop Entry]
Encoding=UTF-8
Version=1.0
Type=Application
Name=ApplicationName
GenericName=ApplicationName
Icon=/home/user/application-icon.png
Exec=/home/user/application/application-executable
Categories=Category;Subcategory

Done!

Removing unused packages in Linux

To remove unused packages in Linux, we will use the following software:

• deborphan
• gtkorphan (GUI based)
• rpmorphan

References

• https://www.ostechnix.com/how-to-find-and-remove-unused-packages-in-linux/

Deleting files specified in a text based file list

To delete a list of files specified in a text based file list, do the following:

> for /f %i in (files_to_delete.txt) do del %i

Reference:
https://superuser.com/questions/355584/how-to-delete-files-from-a-folder-using-a-list-of-file-names-in-windows

Export text based file list for the difference between 2 directories (Windows version)

The following is a tutorial for exporting a text-based file list showing the difference between 2 directories (e.g. D:\DirA, D:\DirB):

Step 1: Create a text-based file list for both directories

> cd D:\DirA
> dir /s /b /a:-d > file-list-dir-a.txt
> cd D:\DirB
> dir /s /b /a:-d > file-list-dir-b.txt

Step 2: Use WinMerge to get the difference between the 2 file lists:

Note: To display difference only, you need to set "View > Diff Context > 0 Lines".

Step 3: Copy the difference from WinMerge and create a text file to store it.

Ubuntu dock shows applications in current workspace only

In Ubuntu dock, to show applications in current workspace only, run the following command:

$ gsettings set org.gnome.shell.extensions.dash-to-dock isolate-workspaces true

References

• https://askubuntu.com/questions/992558/how-can-i-configure-the-ubuntu-dock-to-show-windows-only-from-the-current-worksp
• https://extensions.gnome.org/extension/887/workspace-isolated-dash/

Running Springboot web app in IntelliJ Idea Community Edition

When you run your springboot application in IntelliJ idea Community Edition having the following error, you can try the solution below to solve the problem.

Error "Failed to introspect annotated methods on class org.springframework.boot.web.servlet.support.SpringBootServletInitializer"

If your "pom.xml" has dependency with "provided" scope, you may have trouble when running your application in IntelliJ Idea Community Edition.

<dependency>   

  <groupId>org.springframework.boot</groupId>   

  <artifactId>spring-boot-starter-tomcat</artifactId>   

  <scope>provided</scope>

</dependency>

Some suggests that you can change the scope from "provided" to "compile". Here is another solution for this issue:

In your "Run/Debug Configurations", check "Include dependencies with 'Provided' scope". Then you can run the application from IntelliJ Idea Community Edition.

Image bytes to np array in Python

For reference:

# data - image bytes

im = Image.open(BytesIO(data))
I =  numpy.asarray(im)
print("I type:", type(I), "I shape:", I.shape)

>> I type: <class 'numpy.ndarray'> I shape: (512, 512, 3)