Update L1

Update L4, recursion

Update L4, recursion

Update L20

Update P16

Update L19, L20

Update L19

Update P15 add 'python -m'

Update L18, P15

Update L18, P14

Update L18, P14

Update L16

Update P12

Update L14, L15

Update SQLAlchemy part

Method Query and Http fix

Update L15

Add external pypi

Update OOP

Update OOP