How to create threads

The example show how to define the behavior of a thread and run it.

import threading
import time
import random

class MyThread(threading.Thread):
 def __init__(self, myName):
  threading.Thread.__init__(self)
  self.myName = myName

 def run(self):
  while True:
   time.sleep(random.randint(0,3)) # wait a random time from 0 to 3 secs
   print "My name is",self.myName

thread1 = MyThread("1")
thread1.start() # the thread will run in background
thread2 = MyThread("2")
thread2.start()

My name is 1
My name is 1
My name is 2
My name is 2
My name is 1
...

The two threads will print in the console their attribute myName with random time interval.

How to work with exceptions

Here is:

• How to define an exception
• How to raise an exception
• How to catch an exception

class MyException(Exception): # a custom exception
 """ My own exception class """
 def __init__(self,value):
  self.value = value
 def __str__(self):
  return repr(self.value)

def myFunction(): # this function will raise a exception
 print "The shuttle is landed"
 raise MyException("Huston, we have a problem")

def handleException(): # this function will handle the exception
 try:
  myFunction()
 except MyException, e:
  print "Something is going wrong:", e.value

## test the exception handling ##
handleException();

The shuttle is landed
Something is going wrong: Huston, we have a problem

How to define a class (using inheritance too)

The snippet contains:

• How to declare and use a class with attributes and methods
• How to declare a class using inheritance

class Point2D:
 """ a point in a 2D space """
 name = "A dummy name" # attribute

 def __init__(self,x,y): # constructor
  self.x = x
  self.y = y

 def product(self,p): # method
  """ product with another point """
  return self.x*p.x + self.y*p.y

 def print_2D(self):
  print "(",self.x,",",self.y,")"

class Point3D(Point2D): # Point3D inherit Point2D
 def __init__(self,x,y,z):
  self.x = x
  self.y = y
  self.z = z

 def print_3D(self):
  print "(",self.x,",",self.y,",",self.z,")"

## just test the our classes ##

p2 = Point2D(1,2)
p2.print_2D()
print p2.product(Point2D(2,1))

p3 = Point3D(5,4,3)
p3.print_2D()
p3.print_3D() # inherited method
print p3.name # inherited attribute
print dir(Point2D)
print dir(Point3D) # dir return a list with attribute and methods of the class

( 1 , 2 )
4
( 5 , 4 )
( 5 , 4 , 3 )
A dummy name
['__doc__', '__init__', '__module__', 'name', 'print_2D', 'product']
['__doc__', '__init__', '__module__', 'name', 'print_2D', 'print_3D', 'product']