I would like to clear things here.I am assuming beginner as a common denominator to this post.
len() method is just a shortcut to __len__ magic method .So when you call len() on your own container type ,it does not traverse whole sequence ,it just calls __len__ method and returns value(assume self.size=0 in constructor) from this method.This value incremented or decremented in add and remove method on your container type. Moreover,there can never be length method on iterators - (generators are also iterators,not vice versa).Iterators are meant for traversing a sequence or container,they do not keep track of length..generators are meant to produce infinite items. When you call len(list) or len(deque) or any collection type,they override this __len__ internally or some other similar mechanism .That is very much “similar” to ArrayList here in java. http://grepcode.com/file/repository.grepcode.com/java/root/jdk/openjdk/6-b14/java/util/ArrayList.java the same can be seen here .. http://hg.python.org/cpython/file/ba975c7c33d3/Modules/_collectionsmodule.c To make your type iterable ,you just have to implement __iter__ and next() method,there is no __len__ method here.So you will always receive " there is no len() method your object method".Since you passed generator object to it.you received that error. This whole discussion is equal to IEnumerable<T> and ICollection<T> in C#. python gist is here ,https://gist.github.com/1607183 anybody can test it. Thanks & Regards, Sreenivas Reddy Thatiparthy, 9703888668. "Anyone who has never made a mistake has never tried anything new !!! " --Albert Einstein _______________________________________________ BangPypers mailing list BangPypers@python.org http://mail.python.org/mailman/listinfo/bangpypers
