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New Style classes and inheritance
Objects - Intermediate example from a Well House Consultants training course
More on Objects - Intermediate [link]
Source code: cl_n.py Module: Y112
"""Short demonstration of a group of classes in Python. There's
a base class called "pubtrans" which defines all types of public transport that the application supports, and two derived classes called "bus" and "train" which start off with "pubtrans" as their basis and are then extended to add extra code and replace the code which is in the base class as it applied to most (but not all) piecees of public transport. The demonstration file also includes a short piece of text code to show how it works, and to allow you to run it stand alone to validate that it's been installed correctly and that all dependencies are available. This example uses NEW STYLE CLASSES - the ones that we encourage you to use as they offer an improved design over old style classes that make them easier to maintain, and also they remain avaialble in Python 3.x - which old style classes don't! A full application (rather than just a demo such as this) should include documentation strings, and the test harness would be better written using the doctest or unittest modules""" class pubtrans(object): def __init__(self,about): self.info = about def getabout(self): return self.info def getvehicles(self): return 1 class train(pubtrans): def __init__(self,about,vehicle_capacity,coaches): super(train,self).__init__(about) self.vc = vehicle_capacity self.nc = coaches def getcapacity(self): return self.vc * self.nc def getvehicles(self): return self.nc class bus(pubtrans): def __init__(self,about,vehicle_capacity): super(bus,self).__init__(about) self.vc = vehicle_capacity def getcapacity(self): return self.vc if __name__ == "__main__": testgroup = [train("First Great Western cl 150",80,2)] testgroup.append(bus("First Avon and Somerset",81)) testgroup.append(bus("Faresaver",29)) testgroup.append(train("South West Trains cl 159",75,3)) format = "%-30s %4d %d" tpc = 0 tvc = 0 for option in testgroup: text = option.getabout() pass_count = option.getcapacity() veh_count = option.getvehicles() tpc += pass_count tvc += veh_count print format % (text, pass_count, veh_count) print format % (" --- TOTAL ---",tpc,tvc) Learn about this subject
This module and example are covered on the following public courses:
* Learning to program in Python * Python Programming * Intermediate Python Also available on on site courses for larger groups Books covering this topic
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Other Examples
This example comes from our "Objects - Intermediate" training module. You'll find a description of the topic and some
other closely related examples on the "Objects - Intermediate" module index page.
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