Why do people say that Java is more scalable than python?

Question

I've seen this argument in a few places, and now, recently i saw it again on a reddit post. This is by no means a flame against any of these two languages. I am just puzzled why there is this bad reputation about python not being scalable.
I'm a python guy and now I'm getting started with Java and i just want to understand what makes Java so scalable and if the python setup that I have in mind is a good way to scale large python apps.

Now back to my idea of scaling a Python app. Let's say you code it using Django. Django runs its apps in fastcgi mode. So what if you have a front Nginx server and behind it as many other servers as needed that will each run your Django app in fastcgi mode. The front Nginx server will then load balance between your backend Djnago fastcgi running servers. Django also supports multiple databases so you could write to one master DB and then read from many slaves, again for load balancing. Throw a memcached server in to this mix and there you go you have scalability. Don't you?

Is this a viable setup? What does Java makes better? How do you scale a Java app?

Answer 1

Without getting into a flamewar, consider how Python handles multi-threaded apps as compared to Java? For example, what global locks are in place in both languages that hurt concurrency (hint, Python's GIL - Global Interpreter Lock)?

Answer 2

Scalability is a very overloaded term these days. The comments probably refer to in-process vertical scalability.

Python has a global interpreter lock (GIL) that severely limits its ability to scale up to many threads. It releases it when calling native code (reacquiring it when the native returns), but this still requires careful design when trying to write scalable software in Python.

Answer 3

While I don't agree with the statement, I suppose they think Java is more scalable because it runs a lot faster. The JVM is very efficient (except perhaps in memory usage). Also Python's GIL (Global Interpreter Lock) doesn't allow "real" threading, while Java doesn't have a GIL and has true multithreading.

Answer 4

Hmmm - scalable could mean many things - scalable by distributed architecture, scalable by speed?

On the scalable by speed front, Java generally can process instructions faster than python - for the right kind of problem, much faster (I guess the main reason for that is that Java is compiled whereas Python is interpreted). From that point of view, Java can generally do more with less, and so is more scalable.

I'm referring my source experimental information back to two sources; http://mrpointy.wordpress.com/2007/11/06/java-vs-python-performance/ and http://blog.dhananjaynene.com/2008/07/performance-comparison-c-java-python-ruby-jython-jruby-groovy/

Answer 5

I think this article sums up many of the arguments about scaling and dynamic languages:

http://blogs.tedneward.com/2008/01/24/Can+Dynamic+Languages+Scale.aspx

It's worth noting its two definition for scaling...

1. Size of project, as in lines-of-code (LOC)
2. Capacity handling, as in "it needs to scale to 100,000 requests per second"

One often used argument about any dynamic language scaling is that as the code-base grows it becomes harder to refactor it without IDE support. Due to the lack of type information at compile time this support is often impossible to implement in dynamic languages.

Answer 6

I get mad when I see arguments like this. Not because I get all butthurt about haters harshing my Python mellow, but because to my mind, saying "X doesn't scale" is meaningless. It is necessary to specify a dimension, at the very least.

People are reluctant to do this, as it often reveals the fact that they don't have a good handle on the problem that they're speaking with confidence about. The global interpreter lock is a good touchstone here: threads are not the only way to perform concurrent operations.