[Tutor] Operator Overloading
Following an example from a book, I'm getting an unexpected outcome. The point of exercise is to extend operator overloading methods from a superclass and track the method calls. Here's the code, class MyList: def __init__(self, start): self.wrapped = [ ] for x in start: self.wrapped.append(x) def __add__(self, other): return MyList(self.wrapped + other) def __len__(self): return len(self.wrapped) = from module import MyList class MyListSub(MyList): calls = 0 def __init__(self, start): self.adds = 0 MyList.__init__(self, start) def __add__(self, other): MyListSub.calls = MyListSub.calls + 1 self.adds = self.adds + 1 return MyList.__add__(self, other) def __len__(self): MyListSub.calls = MyListSub.calls + 1 self.adds = self.adds + 1 return MyList.__len__(self) def stats(self): return self.calls, self.adds This is not my code but is taken from the book I'm working with. My problem is that whenever I call to the __add__ method the counters increase by 2 while calls the __len__ method increase the counters by 1 as expected. What I've concluded is that the method which overloads and arithmetic operations executes the counter statements twice while the method which overloads a sequencing operation executes the counter statements only once. Otherwise, I can see no difference between the two methods. Here's an example, >>> A = MyListSub([1, 2, 3]) >>> A.stats() (0, 0) >>> len(A) 3 >>> A.stats() (1, 1) >>> A + [4, 5, 6] [1, 2, 3, 4, 5, 6] >>> A.stats() (3, 3) I'm stumped and and would appreciate any help. Kevin ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Operator Overloading
On Mon, 04 Apr 2005 21:14:21 +1200 John Fouhy <[EMAIL PROTECTED]> wrote: > Are you sure you've giving us all the code? No, I was trying to keep it simple. Anyway, here it is, class MyList: def __init__(self, start): self.wrapped = [ ] for x in start: self.wrapped.append(x) def __add__(self, other): return MyList(self.wrapped + other) def __mul__(self, time): return MyList(self.wrapped * time) def __getitem__(self, offset): return self.wrapped[offset] def __len__(self): return len(self.wrapped) def __getslice__(self, low, high): return MyList(self.wrapped[low:high]) def __setitem__(self, index, value): self.wrapped[index] = value print self.wrapped def __getattr__(self, name): return getattr(self.wrapped, name) def __repr__(self): return `self.wrapped` = from mylist import MyList class MyListSub(MyList): calls = 0 def __init__(self, start): self.adds = 0 MyList.__init__(self, start) def __add__(self, other): MyListSub.calls = MyListSub.calls + 1 self.adds = self.adds + 1 return MyList.__add__(self, other) def __mul__(self, time): MyListSub.calls = MyListSub.calls + 1 self.adds = self.adds + 1 return MyList.__mul__(self, time) def __getitem__(self, offset): MyListSub.calls = MyListSub.calls + 1 self.adds = self.adds + 1 return MyList.__getitem__(self, offset) def __len__(self): MyListSub.calls = MyListSub.calls + 1 self.adds = self.adds + 1 return MyList.__len__(self) def __getslice__(self, low, high): MyListSub.calls = MyListSub.calls + 1 self.adds = self.adds + 1 return MyList.__getslice__(self, low, high) def __setitem__(self, index, value): MyListSub.calls = MyListSub.calls + 1 self.adds = self.adds + 1 return MyList.__setitem__(self, index, value) def __getattr__(self, name): MyListSub.calls = MyListSub.calls + 1 self.adds = self.adds + 1 return MyList.__getattr__(self, name) def __sub__(self, index): MyListSub.calls = MyListSub.calls + 1 self.adds = self.adds + 1 return MyList.__sub__(self, index) def __and__(self, value): MyListSub.calls = MyListSub.calls + 1 self.adds = self.adds + 1 MyList.__and__(self, value) def stats(self): return self.calls, self.adds ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Operator Overloading
On Tue, 05 Apr 2005 10:56:40 +1200 (NZST)
[EMAIL PROTECTED] wrote:
> Fine, but always test the simplified version, unless you're
> absolutely certain what you're throwing out!
Point taken.
> When you do 'A + [4, 5, 6]', python first calls
> A.__getattr__('__coerce__').
Everything's working fine now.
> pdb is useful :-)
Thanks,
Kevin
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[Tutor] Calling a function
I'm having trouble with this code which is meant to run a time
comparison between two similar functions. The first module is
makezeros.py
def lots_of_appends():
zeros = []
for i in range(1):
zeros.append(0)
def one_multiply():
zeros = [0] * 1
The second module is timings.py.
import time, makezeros
def do_timing(num_times, *funcs):
totals = {}
for func in funcs: totals[func] = 0.0
for x in range(num_times):
for func in funcs:
starttime = time.time()
apply(func)
stoptime = time.time()
elapsed = stoptime-starttime
totals[func] = totals[func] + elapsed
for func in funcs:
print "Running %s %d times took %.3f seconds" %
(func.__name__, num_times, totals[func])
do_timing(100, (makezeros.lots_of_appends, makezeros.one_multiply))
Here's the outcome I get:
$ python ./Python/timings.py
Traceback (most recent call last):
File "./Python/timings.py", line 17, in ?
do_timing(100, (lots_of_appends, one_multiply))
File "./Python/timings.py", line 10, in do_timing
apply(func)
TypeError: 'tuple' object is not callable
BTW, the code is taken straight out of Learning Python, but I've
been banging my head on it for awhile. Any ideas??
Kevin
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Re: [Tutor] Calling a function
Ewald & John, thanks for the help. i'll work on it some more with your ideas in mind (after getting some sleep). Kevin ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
[Tutor] fileinput problem
I'm getting unexpected behaviour from this module. My script is meant to count the number of occurences of a term in one or more files. --- import sys, string, fileinput searchterm, sys.argv[1:] = sys.argv[1], sys.argv[2:] for line in fileinput.input(): num_matches = string.count(line, searchterm) if num_matches: print "found '%s' %i times in %s on line %i." % (searchterm, num_matches, fileinput.filename(), fileinput.filelineno()) --- When I run at the command line, this error message appears: $ python ./Python/fileinput.py for ./Python/*.py Traceback (most recent call last): File "./Python/fileinput.py", line 1, in ? import sys, string, fileinput File "./Python/fileinput.py", line 6, in ? for line in fileinput.input(): AttributeError: 'module' object has no attribute 'input' --- I'm stumped. Any ideas? Kevin ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] fileinput problem
On Sat, 25 Jun 2005 06:41:01 -0400 Kent Johnson <[EMAIL PROTECTED]> wrote: > You named your program fileinput.py, so when you import fileinput > you are getting your own program again instead of the library > module. Change the name of your program and try again. Doh! I do remember reading that somewhere before. Lesson learnt. Kevin ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
[Tutor] Single Underscore
What's the significance of naming a variable with a single underscore as its first character? For example, I'm looking at find.py in the standard library and it has variables named _debug and _prune. Kevin ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Single Underscore
Thanks for the info. I'll look into the links provided. > http://jaynes.colorado.edu/PythonGuidelines.html > http://www.python.org/peps/pep-0008.html Kevin ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
