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    <p>I actually think you'd be best off with kryo (I'm not aware of alternatives that offer less schema defining other than non-binary protocols). You mention that pickle is not susceptible to the slowdowns and bloat that kryo gets without registering classes, but kryo is still faster and less bloated than pickle even without registering classes. See the following micro-benchmark (obviously take it with a grain of salt, but this is what I could do easily):</p> <h2>Python pickle</h2> <pre><code>import pickle import time class Person: def __init__(self, name, age): self.name = name self.age = age people = [Person("Alex", 20), Person("Barbara", 25), Person("Charles", 30), Person("David", 35), Person("Emily", 40)] for i in xrange(10000): output = pickle.dumps(people, -1) if i == 0: print len(output) start_time = time.time() for i in xrange(10000): output = pickle.dumps(people, -1) print time.time() - start_time </code></pre> <p>Outputs 174 bytes and 1.18-1.23 seconds for me (Python 2.7.1 on 64-bit Linux)</p> <h2>Scala kryo</h2> <pre><code>import com.esotericsoftware.kryo._ import java.io._ class Person(val name: String, val age: Int) object MyApp extends App { val people = Array(new Person("Alex", 20), new Person("Barbara", 25), new Person("Charles", 30), new Person("David", 35), new Person("Emily", 40)) val kryo = new Kryo kryo.setRegistrationOptional(true) val buffer = new ObjectBuffer(kryo) for (i &lt;- 0 until 10000) { val output = new ByteArrayOutputStream buffer.writeObject(output, people) if (i == 0) println(output.size) } val startTime = System.nanoTime for (i &lt;- 0 until 10000) { val output = new ByteArrayOutputStream buffer.writeObject(output, people) } println((System.nanoTime - startTime) / 1e9) } </code></pre> <p>Outputs 68 bytes for me and 30-40ms (Kryo 1.04, Scala 2.9.1, Java 1.6.0.26 hotspot JVM on 64-bit Linux). For comparison, it outputs 51 bytes and 18-25ms if I register the classes.</p> <h2>Comparison</h2> <p>Kryo uses about 40% of the space and 3% of the time as Python pickle when not registering classes, and about 30% of the space and 2% of the time when registering classes. And you can always write a custom serializer when you want more control.</p>
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    1. POSimple, hassle-free, zero-boilerplate serialization in Scala/Java similar to Python's Pickle?
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    1. USMike
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    1. COThanks for the numbers. I can't seem to deserialize the objects, though, which is a severe limitation (updated my question with this). I get "com.esotericsoftware.kryo.SerializationException: Unable to deserialize object of type: Person" caused by "com.esotericsoftware.kryo.SerializationException: Class cannot be created (missing no-arg constructor): Person".
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    2. COIf you're using a sun/oracle jvm you can use https://github.com/magro/kryo-serializers for deserializing objects without a 0-arg constructor: just change "new Kryo" to "new KryoReflectionFactorySupport".
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    3. CO@MartinGrotzke: You have made me a very happy person today. Impressive work. I see myself pimping around your library already. I really hope it makes its into kryo itself.
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