Comments¶

1. data-diff is similar tool which efficiently diff rows across two different databases.

Installation¶

General Tips¶

1. The method subprocess.run is preferred over older high-level APIs (subprocess.call, subprocess.check_call and subprocess.check_output). The method subprocess.Popen (which powers the high-level APIs) can be used if you need advanced controls. When running a shell command using subprocess.run,

   1. Avoid using system shell (i.e., avoid using shell=True) for 2 reasons. First, avoid shell injection attack. Second, there is no need for you to manually escape special characters in the command.

Execuation Order¶

A SQL statement selects rows and columns from a big (rectangular) table. You put columns that you want to select after SELECT and rows you want to select after FROM. A SQL statement is executed as follows. First, the (INNER|LEFT|RIGHT|FULL) JOIN (ON) is executed if any (see more explanation later). Second, the WHERE

Convert a Video to MP4 Using python-opencv¶

The code below converts a MOV vidoe file to a MP4 vidoe file using OpenCV in Python.

Tips and Traps¶

1. Most videoes have a FPS of 24. Some videos have higher FPS (e.g., 30 or 60) so that they can capture motions better. A record video on a computer has a FPS of the refresh rate of the monitor, which is usually 60. You can get the FPS of a video using OpenCV in Python.