Review Answers

What problems do operating systems solve?

1. Hardware abstraction: interact with heterogeneous hardware through a common interface.
2. Multitasking: Run several programs concurrently, managing their state independently. Programs managed by operating systems are sometimes called applications (hence the neologism app).

What is a system shell?

A system shell is a command-line interface to the operating system, presented through a program called a terminal emulator (usually shortened to terminal).

What is an interpreter?

An interpreter is a program, managed by the OS, that translates human-readable source code into executable machine code, and executes it.

What is the python shell command?

The python command tells the OS to start the python interpreter, which is an application that is managed by the OS. The python interpreter has two modes of operation.

It can launch an interactive shell:

$ python

It can run a script non-interactively:

$ python myscript.py

Note: The $ symbol is a convention used to denote shell input. It is not typed into the terminal.

Review: Our Tools

1. What is atom ?

Atom is a text editor. It edits text, and nothing else.

2. What is ipython and why should it be preferred over python?

IPython is an interactive python shell. It behaves similarly to the python command, but includes nice features for programmers including:

• colorized tracebacks (we’ll talk about those later)
• ? syntax for documentation
• tab-completion
• % syntax for “magic” commands (we’ll talk about those later, too)

Programming in Python

Points to get across:

1. Programming languages impose a structure on your reasoning
2. Such approaches are called “programming paradigms”
3. Python’s programming paradigm is OOP

On OOP:

Metaphorical level

1. Objects are the basic unit of python code
2. Objects are typed
3. Type tells you something about how you should use the object

Practical level

1. Introduce duck-typing: “What can my object do?”
   • Check the methods
   • Use the docs
2. Demonstrate function and caveats for each type.
3. Take Questions

Control Structures

Straightforward. Demonstrate and emphasize = vs ==