Is Python overhyped (just like Java)?

Alex Martelli aleax at aleax.it
Sun Mar 30 00:53:56 CET 2003


Ajay na wrote:

> Can some-one please explain why one would want to use Python?

One word: *PRODUCTIVITY*.

> What is wrong with C++?

One word: *COMPLEXITY*.


> In my opinion, the problem with C++ has nothing to with the language
> semantics.  The problem is that when people are confronted with a powerful
> language like C++, they tend to want to optimize everything to death.
> That's when they get themselves in trouble.

You're over-generalizing.  Not all users of C++ are so naive as to
have failed to read Knuth -- "Premature optimization is the root of
all evil in programming".  But the point is -- by choosing a lower
level language, like C++, at the start of your project, rather than
a higher level one, like Python, you ARE optimizing WAY prematurely.


> Those who use Python know they are sacrificing a lot in terms of memory
> and
> speed.  But if they took the same attitude toward C++, they can actually
> get a lot of flexibility, code reuse, simplicity, and all the other
> benefits of
> OO programming at over half the cost of using Python!  The problem is that

Whaddya mean "over half the cost"?

I'm putting the final touches on a talk I'll give to PythonUK next
week (it's held together with the ACCU conference) on "Python for
C++ and Java programmers".  One example I give is a task for which
C++ is quite suited, with its standard library -- reading a text file,
breaking it into whitespace-separated 'words', building an index from
each word to the line numbers on which it appears, and showing the
index with words in alphabetical order, one per line, each followed
by the line numbers on which it appears.

Thanks to the excellent support given for these tasks by the standard
library, the C++ source is ONLY twice as big as the Python source for
the same job (a more usual ratio is around 5:1).  This holds for both
the simplest versions, and the slightly more complicated ones with
somewhat better optimization.  The runtimes on my box (Linux Mandrake
9.0, gcc 3.1, Python 2.3) are, when the programs are run on the 4.4 MB
of the "King James Bible" in plain ASCII text: 17.4 seconds for the
simplest C++, going down to 15 with optimizations; 11.2 seconds for the
simplest Python, going down to 8.1 with optimizations (CPU times are
in very similar ratios).  Of course, this basically reflects the
excellence of Python's intrinsics (dictionaries, lists, strings)
versus the lesser quality of C++'s library implementation (maps,
vectors, strings) -- with different implementations, you may see
different ratios.

But what won't change is, the Python program IS smaller, because
Python it's a higher-level language -- AND each statement is
intrinsically cleaner and simpler, so the development time ratio,
for programmers who have perfectly mastered both languages and
the respective standard libraries, is even more extreme than the
ratio in program sizes.  The simplest and most flexible C++ you
can write is still way bigger, more complicated, and less flexible
than the most refined and optimized Python code it may make sense
to write -- it's as simple as this.  For tasks to which Python is
extremely well suited (text processing of all kinds, including XML
parsing, for example), you may ALSO get better running time than
C++ with the standard library would give you -- in general, C++
lets you develop faster code, but oh what a price in terms of
productivity you pay for that!

And the funniest thing is, there IS no need to pay that price --
90% of your program's runtime is likely to be taken up by 10%
of your program's source code, or some such ratio.  By writing
Python first, you'll often get an application with acceptable
performance; if not, you profile it, find out the hot-spots,
optimize those in Python terms, and if that's still not enough,
it's EASY to recode the hot-spots in faster ways while still
leaving MOST of your application in Python.  There are many
ways to do such recoding (even without counting the still
experimental 'psyco' selective just-in-time optimizer), and
among them are ways to integrate C++, such as SciPy's "weave"
and the Boost Python Library (if you don't know Boost, DO
give it a look -- it WILL increase your C++ productivity, and
not just by easing integration of C++ to Python, either).

> people who don't understand C++, are afraid to use the 'virtual' features
> of
> that language because it's 'too expensive'.  But that's stupid...because
> Python's 'virtualness' is even more expensive!

It's quite inconsiderate of you to imply that Python users are
"people who don't understand C++", when among those users are
people like Andrew Koenig (author of "Ruminations on C++" and
other great C++ books, as well as a towering figure of C++
development -- the algorithm for name lookup in the C++ language
is called "Koenig lookup" because HE developed it...!), Bruce
Eckel (author of best-sellers "Thinking in C++" and "Thinking
in Java"), and so many others whose C++ competence is in all
likelihood AT LEAST as good as yours.


> Nope...I'm not trolling...I want someone to give a solid and intelligent
> argument about why I should switch from C++ to Python!

You shouldn't *SWITCH*!  If you hadn't already made the huge
investment to master all the complexity of C++, it might be
best to avoid it -- but, if you HAVE made it, count it as a
"sunk cost", as I do, and see how best to leverage it.  Learn
Python (a trivial investment compared to learning C++), and
use BOTH Python and C++ in your development.  You'll find that
Python gives you extremely high productivity and flexibility,
letting you prototype, experiment, refactor whole architectures
from the inside out and back again -- even if you knew the
final product MUST be delivered in C++ due to contractual
requirements, you'd STILL be better off doing the early phases
in Python ANYWAY.  Once the program is working, benchmark it;
most often, you'll find you're done -- in a FRACTION of the
time.  If the performance isn't satisfactory, profile it, and
start optimizing -- including recoding parts in C++, e.g.
with weave or the Boost Python Library.  In the end, you'll use
both Python and C++ in the same program, *each for what it does
best*: Python for most of the code, C++ for the bottlenecks.
It's as simple as this, really!

And your programming productivity will soar...


Alex





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