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inheritance, factory, decorator, comparators, static methods, caching, etc
Code testing, patterns, profiles and optimisation. example from a Well House Consultants training course
More on Code testing, patterns, profiles and optimisation. [link]
Source code: travel.py Module: Y212
#!/usr/bin/env python
# inheritance, factory, decorator, comparators, static methods # import, exceptions, stderr, sys, object state caching import sys # An example from some more advanced object training ... covercount = {} def coverage(why): # define how to wrap the function call myname = why.func_name def wrapped(*args, **kwargs): # Do the original stuff (of course?) finalanswer = why(*args, **kwargs) # Extra bits to be performed ... sofar = covercount.get(myname,0) covercount[myname] = sofar + 1 return finalanswer # pass back the wrapped function # and pass back the wrapped docstring too wrapped.__doc__ = why.__doc__ return wrapped def coverage_report(): print "\nHow many times each method was called:" for func in covercount.keys(): print covercount[func],func class travel(object): @coverage def __init__(self,defstring): type, self.leaves, self.destiny, \ self.carpacity, self.duration = defstring.split('\t') self.cars = 1 self.cached = False self.regulator = "Maritime agency" def getdest(self): return self.destiny getdest = coverage(getdest) @coverage def getcars(self): return int(self.cars) @coverage def getadmins(self): return self.getpeeps() * int(self.duration) @coverage def more_opportunities(this,that): val = cmp(this.getadmins(), that.getadmins()) if (val > 0): return this return that @staticmethod @coverage def most_opportunities(possibilities): try: so_far = possibilities[0] except: raise for maybe in range(1,len(possibilities)): so_far = so_far.more_opportunities(possibilities[maybe]) return so_far @staticmethod @coverage def factory(line): have = None if line.startswith("train\t"): have =train(line) elif line.startswith("bus\t"): have = bus(line) elif line.startswith("floating bridge\t"): have = ferry(line) if not have: # exits function on "raise", no value returned # raise creates an exception object raise TypeError, "Not a valid travel mode" return have @coverage def getpeeps(self): if not self.cached: self.peeps = int(self.carpacity) * int(self.cars) self.cached = True return self.peeps @coverage def __str__(self): itsa = self.__class__.__name__ passes = self.getpeeps() return "A " + "%-8s" % itsa + " with space for " + \ "%4d" % passes # set up an attribute called "people". # use the getpeeps method to read, and None to write people = property(getpeeps,None) class train (travel): @coverage def __init__(self,defstring): type, self.leaves, self.destiny, self.cars, \ self.carpacity, self.duration = defstring.split('\t') self.cached = False self.regulator = "ORR" class roadie (travel): pass class bus (roadie): @coverage def __init__(self,defstring): # travel.__init__(self, defstring) # Above is deprecated - use the following: super(bus,self).__init__(defstring) self.regulator = "DfT" @coverage def getpeeps(self): if not self.cached: self.peeps = int(self.carpacity) - 1 self.cached = True return self.peeps class ferry(travel): pass # --------------------------------------------------------- if __name__ == "__main__": params = sys.argv if len(params) < 2: fh = sys.stdin else: try: fh = open(sys.argv[1]) except IOError, e: sys.stderr.write("Error 1543: Can't open "+sys.argv[1]+" for read: ") sys.stderr.write(e.strerror + "\n") # Do not recussitate ;-) sys.exit(1) except StandardError, e: sys.stderr.write("Error 1544: Dallas, we have an unusual problem\n") sys.stderr.write("And it's a "+ e.__class__.__name__ + "\n") sys.exit(1) options = [] for line in fh: try: options.append(travel.factory(line)) except: pass summery = "\n" for option in options: if option.getpeeps() < 50: continue # strong suggestion - hide the formatting in the class print "%2d" % (option.getcars()), \ "%-15s" % option.getdest(), \ "%3d" % option.getpeeps() print "%2d - %15s - %10s - %3d - %3d" % (option.getcars(), \ option.getdest(), \ option.regulator, \ option.people, \ option.getpeeps()) summery += str(option) + "\n" # print option print summery # Comparators try: first = options[3] second = options[5] print first print second print first.getadmins() print second.getadmins() sellon = first.more_opportunities(second) print sellon except: sys.stderr.write("Error 5544: you are short of data for comparators\n") try: sellon = travel.most_opportunities(options) print sellon except: sys.stderr.write('Error 5432: not even enough data for "most" test!!\n') # Look at use of code coverage_report() """ -------------------------------------------------------------- Sample data file: train 07:17 Swindon 2 72 25 train 06:40 Southampton 2 71 89 train 19:11 Southampton 1 71 97 train 19:47 Cheltenham Spa 3 75 65 floating bridge 22:30 Hoek van Holland 1200 480 bus 07:24 Chippenham 62 24 bus 08:04 Bath 41 37 bus 08:07 Bath 61 35 floating bridge 09:20 Amsterdam 400 5 elephant 10:40 Atworth 5 45 ------------------------------------------------------------------ Runs like this: munchkin:ps grahamellis$ ./travel.py journey.txt 2 Swindon 144 2 - Swindon - ORR - 144 - 144 2 Southampton 142 2 - Southampton - ORR - 142 - 142 1 Southampton 71 1 - Southampton - ORR - 71 - 71 3 Cheltenham Spa 225 3 - Cheltenham Spa - ORR - 225 - 225 1 Hoek van Holland 1200 1 - Hoek van Holland - Maritime agency - 1200 - 1200 1 Chippenham 61 1 - Chippenham - DfT - 61 - 61 1 Bath 60 1 - Bath - DfT - 60 - 60 1 Amsterdam 400 1 - Amsterdam - Maritime agency - 400 - 400 A train with space for 144 A train with space for 142 A train with space for 71 A train with space for 225 A ferry with space for 1200 A bus with space for 61 A bus with space for 60 A ferry with space for 400 A train with space for 225 A bus with space for 61 14625 1464 A train with space for 225 A ferry with space for 1200 How many times each method was called: 12 __str__ 9 factory 65 getpeeps 1 most_opportunities 9 more_opportunities 16 getcars 20 getadmins 12 __init__ 16 getdest munchkin:ps grahamellis$ ----------- Another sample -------------- munchkin:ps grahamellis$ ./travel.py ^D Error 5544: you are short of data for comparators Error 5432: not even enough data for "most" test!! How many times each method was called: munchkin:ps grahamellis$ """ Learn about this subject
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