Interesting talk on Python vs. Ruby and how he would like Python to have just a bit more syntactic flexibility.
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From: Gregory Ewing on 19 Feb 2010 00:52 Steve Howell wrote: > Python may not support the broadest notion of anonymous functions, but > it definitely has anonymous blocks. You can write this in Python: > > for i in range(10): > print i > print i * i > print i * i * i There's a clear difference between this and a Ruby block, however. A "block" in Ruby is implemented by passing a callable object to a method. There is no callable object corresponding to the body of a for-loop in Python. The important thing about Ruby blocks is not that they're anonymous, but that they're concrete objects that can be manipulated. The Ruby approach has the advantage of making it possible to implement user-defined control structures without requiring a macro facility. You can't do that in Python. However, there's something that Python's iterator protocol makes possible that you can't do with a block-passing approach. You can have multiple iterators active at once, and pull values from them as an when required in the calling code. Ruby's version of the iterator protocol can't handle that, because once an iterator is started it retains control until it's finished. Also, most people who advocate adding some form of block-passing facility to Python don't seem to have thought through what would happen if the block contains any break, continue, return or yield statements. This issue was looked into in some detail back when there was consideration of implementing the with-statement by passing the body as a function. Getting these statements to behave intuitively inside the body turned out to be a very thorny problem -- thorny enough to cause the block-passing idea to be abandoned in favour of the current implementation. -- Greg |