Hacker News new | ask | show | jobs
by ferrari8608 3652 days ago
I've never understood why that phrase applies to Python when the language still has the map, filter, reduce, etc. functional functions. Generators and comprehensions completely removed the need for those, yet the functions remain even in Python 3.

On the subject of printing, there are actual reasons for having this duplicate functionality. The main way to print is of course the print function in three, or print statement in two. The print function was lacking the ability to flush the buffer before that was introduced in three. You would have to call sys.stdout.flush(), whereas now the print function includes the boolean "flush" keyword argument. The second way to print is to call sys.stdout.write(), which does not automatically append a newline. That functionality was implemented in the print function with the "end" keyword argument. You can pass it an empty string in place of the newline.

So for most use cases, print() is just fine. Sometimes you want finer grained control, and for that you would use the sys module.
2 comments
drostie 3652 days ago
Python 3 at least changes the semantics of map and filter so that they are generators.

Lazy sequences are the sort of thing that you don't care about until you need to process a ten-million-line file (or whatever) and suddenly find that your program is slowing down for pointless memory allocations up-front -- then they become unbelievably important.

link
ferrari8608 3652 days ago
Yes, you are absolutely correct. In our production code, which is currently running 2.7, we make extensive use of the itertools versions of those functions (imap, ifilter, etc.) for this reason. The itertools functions behave exactly like the Python 3 builtins, as iterators. The memory footprint is minimal, and they are just overall faster.
link
fao_ 3652 days ago
> Generators and comprehensions completely removed the need for those, yet the functions remain even in Python 3.

Hmm, I had never thought about it like that. Are there any articles, etc. you recommend about the differences or the advantages of one method over the other? It'd be nice to look into this more.

link
nomel 3651 days ago
I don't think you'll find one. Guido wanted to remove them [1], but people wanted them to stay for some reason.

There is no difference between `map(func, values)` and `[func(x) for x in values]`, except for character count.

[1] http://www.artima.com/weblogs/viewpost.jsp?thread=98196

link