Jonathan Huelman

CSC 415 – Programming Languages

Python

Introduction to Python

Named for Monty Python’s Flying Circus, the British sketch comedy TV show

Defined as a very high-level scripting language, there isn’t a lot Python

can’t do with it’s extensive standard library

Python is interpreted, meaning each line is indirectly executed.

There is no byte code

“Batteries included”

History of Python

Guido Van Rossum, BDFL (Benevolent Dictator For Life)

Python based on ABC, first created in the late 1980s

The Python Software foundation launched in March 2006 with Van Rossum as President. It is a non-profit organization dedicated to the Python programming language

Release dates for the major versions:Python 1.0 - January 1994

Python 2.0 - October 16, 2000Python 3.0 - December 3, 2008

Who Uses Python

Graphics Industrial Light and Magic Walt Disney Feature Animation

Games Battlefield 2 Civilization 4

Web Development Yahoo Maps Google Linux Weekly News

Mathematical libraries Matplotlib, which is like MATLAB NumPy, a language extension that adds

support for large and fast, multi-dimensional arrays and matrices

PyIMSL Studio is a Python distribution which includes the IMSL Numerical Libraries.

The Zen of Python

>>> import this

The Zen of Python, by Tim Peters

Beautiful is better than ugly.

Explicit is better than implicit.

Simple is better than complex.

Complex is better than complicated.

Flat is better than nested.

Sparse is better than dense.

Readability counts.

Special cases aren't special enough to break the rules.

Although practicality beats purity.

Errors should never pass silently.

Unless explicitly silenced.

In the face of ambiguity, refuse the temptation to guess.

There should be one-- and preferably only one --obvious way to do it.

Although that way may not be obvious at first unless you're Dutch.

Now is better than never.

Although never is often better than *right* now.

If the implementation is hard to explain, it's a bad idea.

If the implementation is easy to explain, it may be a good idea.

Namespaces are one honking great idea -- let's do more of those!

>>>

‘Pythonic’ Code

1. for (i=0; i < mylist_length; i++)

{ do_something(mylist[i]); }

2. i = 0 while i < mylist_length: do_something(mylist[i]) i += 1

3. for i in range(mylist_length): do_something(mylist[i])

4. for element in mylist: do_something(element)

The Size of Python

http://docs.python.org/library/

Example – Regular Expressions

More Examples

http://wiki.python.org/moin/SimplePrograms

http://code.activestate.com/recipes/577905-password-generator/?in=lang-python

Primes program

beers on the wall and a more ‘pythonic’ version

Guessing game

Pros on Python

Why Reddit uses Python“The biggest thing that has kept us on Python … ...

One are the libraries. There’s a library for everything. We’ve been learning a lot of these technologies and a lot of these architectures as we go.

The other thing that keeps us on Python, and this is the major thing, is how readable and writable it is. When we hire new employees ... it’s awesome because I can see from across the room, looking at their screen, whether their code is good or bad. Because good Python code has a very obvious structure.”

- Steve Huffman, Web Developer, Co-Founder of Reddit.com

Evaluation

very clear, readable syntax, once you get used to the fact that indentation is key to syntax

intuitive object orientation natural expression of procedural code full modularity, supporting hierarchical packages exception-based error handling very high level dynamic data types extensive standard libraries and third party modules for

virtually every task embeddable within applications as a scripting interface free, with relatively cheap IDEs available on the Internet

Sources

http://faassen.n--tree.net/blog/view/weblog/2005/08/06/0

http://brainsik.theory.org/.:./2009/why-reddit-uses-python

http://www.yak.net/fqa/171.html

http://www.python.org/

http://en.wikipedia.org/wiki/Python_(programming_language)