On Sep 2, 4:09 pm, Ian Kelly <ian.g.ke...@gmail.com> wrote: > On Fri, Sep 2, 2011 at 10:59 AM, Travis Parks <jehugalea...@gmail.com> wrote: > > Hello: > > > I am working on an algorithms library. It provides LINQ like > > functionality to Python iterators. Eventually, I plan on having > > feaures that work against sequences and mappings. > > > I have the code up athttp://code.google.com/p/py-compass. > > > This is my first project in Python, so I'd like some feedback. I want > > to know if I am following conventions (overall style and quality of > > code). > > Sure, here are my comments. > > In the "forever" and "__forever" functions, your use of the term > "generator" is confusing. "__forever" is a generator function, > because it has a yield statement. Its argument, called "generator", > appears to be a callable, not a generator or even necessarily a > generator function. Also, note that __forever(lambda: value) is > functionally equivalent to the more efficient itertools.repeat(value). > > The staticmethod __next(iterator) accesses the class it is defined in, > which suggests that it might be better written as a classmethod > __next(cls, iterator). > > Each of the LINQ-style methods is divided into two parts: the public > method that contains the docstring and some argument checks, and a > private staticmethod that contains the implementation. I'm not > certain what the purpose of that is. If it's to facilitate overriding > the implementation in subclasses, then you need to change the names of > the private methods to start with only one _ character so that they > won't be mangled by the compiler. > > The comments before each method that only contain the name of the > immediately following method are redundant. > > aggregate: the default aggregator is unintuitive to me. I would make > it a required field and add a separate method called sum that calls > aggregate with the operator.add aggregator. > Also, the implementation doesn't look correct. Instead of passing in > each item to the aggregator, you're passing in the number of items > seen so far? The LINQ Aggregate method is basically reduce, so rather > than reinvent the wheel I would suggest this: > > # MISSING is a unique object solely defined to represent missing arguments. > # Unlike None we can safely assume it will never be passed as actual data. > MISSING = object() > > def aggregate(self, aggregator, seed=MISSING): > if seed is self.MISSING: > return reduce(aggregator, self._iterable) > else: > return reduce(aggregator, self._iterable, seed) > > Note for compatibility that in Python 3 the reduce function has been > demoted from a builtin to a member of the functools module. > > any: the name of this method could cause some confusion with the "any" > builtin that does something a bit different. > > compare: the loop would more DRY as a for loop: > > def __compare(first, second, comparison): > for firstval, secondval in itertools.izip_longest(first, second, > fillvalue=self.MISSING): > if firstval is self.MISSING: > return -1 > elif secondval is self.MISSING: > return 1 > else: > result = comparison(firstval, secondval) > if result != 0: > return result > return 0 > > concatenate: again, no need to reinvent the wheel. This should be > more efficient: > > def concatenate(self, other): > return extend(itertools.chain(self.__iterable, other)) > > equals: could be just "return self.compare(other, comparison) == 0" > > __last: the loop could be a for loop: > > # assume we're looking at the last item and try moving to the next > item = result.Value > for item in iterator: pass > return item > > lastOrDefault: there's a lot of repeated logic here. This could just be: > > def lastOrDefault(self, default=None): > try: > return self.last() > except ValueError: > return default > > map / forEach: .NET has to separate these into separate methods due to > static typing. It seems a bit silly to have both of them in Python. > Also, map would be more efficient as "return itertools.imap(mapper, > self.__iterable)" > > max / min: it would be more efficient to use the builtin: > def max(self, key): > return max(self.__iterable, key=key) > If somebody really needs to pass a comparison function instead of a > key function, they can use functools.cmp_to_key. > > randomSamples: a more canonical way to pass the RNG would be to pass > an instance of random.Random rather than an arbitrary function. Then > to get a random integer you can just call generator.randrange(total). > Note that for the default you can just use the random module itself, > which provides default implementations of all the Random methods. > Also, for loops: > > def __randomSamples(iterable, sampleCount, generator): > samples = [] > iterator = iter(iterable) > # fill up the samples with the items from the beginning of the > iterable > for i, value in zip(xrange(sampleCount), iterator): > samples.append(value) > # replace items if the generated number is less than the total > total = len(samples) > for value in iterator: > total += 1 > index = generator.randrange(total) > if index < len(samples): > samples[index] = result > return samples > > __reverse: you could just "return reversed(list(iterable))" > > __rotateLeft: > def __rotateLeft(iterable, shift): > iterator = iter(iterable) > front = list(itertools.islice(iterator, shift)) > return itertools.chain(iterator, front) > > skipWhile: suggest using itertools.dropwhile > take: suggest using itertools.islice > takeWhile: suggest using itertools.takewhile > __toList: "return list(iterable)" > __toSet: "return set(iterable)" > __toTuple: "return tuple(iterable)". Note that as currently written > this actually returns a generator, not a tuple. > __where: suggest using itertools.ifilter > __zip: suggest using a for loop over itertools.izip(first, second) > > Lookup: is inconsistent. The overridden __iter__ method returns an > iterator over the values of the groups, but all the inherited methods > are going to iterate over the keys. Probably you want to pass > groups.values() to the superclass __init__ method. > > Cheers, > Ian
Awesome tips. I appreciate the time you spent commenting on just about every function. I really like your suggestions about using itertools more, and for loops. I was feeling like some things were becoming way too complicated. I also noted the bugs you discovered. I will incorporate your suggestions. Thanks again! -- http://mail.python.org/mailman/listinfo/python-list
