Installation¶
Hands on the Python module subprocess
General Tips¶
The method
subprocess.run
is preferred over older high-level APIs (subprocess.call
,subprocess.check_call
andsubprocess.check_output
). The methodsubprocess.Popen
(which powers the high-level APIs) can be used if you need advanced controls. When running a shell command usingsubprocess.run
,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.
Hands on pathlib.Path
Understand Execuation of SQL Statements
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 Format of Videos Using Using Python
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.