(9)
question mark ? will only match 1 letter. `ls clas?` will list files in the class directory.

(10)
the first line of the script
#!/usr/bin/python
can be replaced by
#!/usr/bin/env python
if you don't know the path of python

(11)
Curly braces {} - Whenever you have a common substring in a series of commands, you can use curly braces for bash to expand this automatically. This comes in very handy when moving or converting files.

#systemprogramming #shell