Python MiniCourse

1
Python Mini-Course

• Part 2 Object-Oriented Python
• Prof Ken Hawick, 2009

2
Syntax Reminders

• !/usr/local/bin/python
• import sys
• z complex(1.0,1.0)
• print z
• print '------------------
• t (1.0,)
• t (3.0,)
• print t
• l 1,2,3
• l2 7,8,9
• l l2
• print l

• d "apples"1, "pears"42, "bananas" 0
• print d"apples"
• print "a" "b",
• print "Hahha"
• assert 1 gt 2, foobar"
• print gtgt sys.stdout, '------------------'

3
More Python Syntax Examples

• def myfunc(a,b,c)
• return a b c
• f myfunc( "apples", "", "pears" )
• x myfunc( 1,2,3)
• print f, x
• print "Hello Ken, enter some text"
• s raw_input("gt ")
• gets line from std input with prompt
• print s
• print float(s)
• causes an error if not a float number

4
Object-Oriented Python

• class classname block
• class classname(base-classes) block
• anInstance MyClass()
• def myMethod(self,nextParameter) block
• __init__ is constructor method
• __name__ is classname identifier string
• __bases__ is tuple of base class objects
• __doc__ is the docstring

5
Python Class Example

• !/usr/local/bin/python
• class Fred defines the class
• x 42.0
• def bill(self) first arg is always
  object's self-reference
• print "Hello from Bill\n" str( Fred.x
  )
• -------------------------------------------------
  --------------------------------------------------
  --
• f Fred() instantiates a Fred
• f.bill() invokes the bill method

6

• !/usr/local/bin/python
• -------------------------------------------------
  ------------
• class Startibartfast
• def hello(self)
• print "Hello from Slartibartfast's hello
  method"
• -------------------------------------------------
  ------------
• class Arthur
• def hello(self)
• print "Hello from Arthur's hello
  method\n"
• return None
• def doSomething(self, a )
• print "this is Arthur's doSomething
  method\n" str(a)
• return None
• -------------------------------------------------
  ------------

• class Ford( Startibartfast, Arthur )
• x 42.0
• def prefect(self)
• print "Hello from prefect\n" str(
  Ford.x )
• -------------------------------------------------
  ------------
• f Ford()
• f.prefect()
• f.hello()
• f.doSomething( 12345.001 )
• gt python test02.py
• Hello from prefect
• 42.0

7
Python has Multiple Inheritance

• Supposed to work left to right etc depending on
  order of base classes search order is BFS
• Built-in object type is ancestor of all objects
  and has some special methods defined.

8
Python Exceptions

• try
• statement(s)
• except expression , target
• statement(s)
• else
• statement(s)
• finally
• statement(s)
• Target is optional identifier name of the
  exception
• ZeroDivisionError TypeError

9
Other Python factoids

• Large library of special methods
• Lots of modules you can download
• Python is good for
• Systems admin tasks user interfaces XML
  network programming web programming distributed
  programming introspective programming.
• It also supports some functional and logic
  programming ideas

10
More Information on Python

• Python in a Nutshell , Alex Martelli, Pub.
  OReilly
• Python Cookbook, Alex Martelli, Anna Martelli
  Ravenscroft and David Ascher, Pub. OReilly
• http//www.python.org
• http//docs.python.org/tutorial/