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Pickle - Java and .NET library for Python's pickle serialization protocol

Pickle is written by Irmen de Jong (irmen@razorvine.net). This software is distributed under the terms written in the file LICENSE.

The pickle serialization protocol

This is a feature complete pickle protocol implementation. You can read and write pickle files. Pickle is Python's serialization protocol.

Java: from Maven, group id net.razorvine artifact id pickle.
.NET: nuget Razorvine.Pickle; https://www.nuget.org/packages/Razorvine.Pickle/

Pickle protocol version support: reading: 0,1,2,3,4,5; writing: 2. We can read all pickle protocol versions (0 to 5, so this includes the latest additions made in Python 3.8 related to out-of-band buffers). We always writes pickles in protocol version 2. There are no plans on including protocol version 1 support. Protocols 3 and 4 contain some nice new features which may eventually be utilized (protocol 5 is quite obscure), but for now, only version 2 is used.

Size limitations

Unlike Python where the length of strings and (byte)arrays is only limited by the available memory, Java and .NET do have an arbitrary maximum object size. The maximum length of strings and byte arrays of both platforms is limited to 2 gigabytes (2^31 - 1). This is not a Pickle library limitation, this is a limitation of the underlying platform. If an object in your pickle exceeds this limit the code will crash with something like an NegativeArraySizeException, OverflowException or perhaps an out of memory error of some sort. You should make sure in your own code that the size of the pickled objects does not exceed 2 gigabyte.

Type Mapping

Python to Java (unpickling)

The Unpickler simply returns an Object. Because Java is a statically typed language you will have to cast that to the appropriate type. Refer to this table to see what you can expect to receive.

PYTHON	JAVA
None	null
bool	boolean
int	int
long	long or BigInteger (depending on size)
string	String
unicode	String
complex	net.razorvine.pickle.objects.ComplexNumber
datetime.date	java.util.Calendar
datetime.datetime	java.util.Calendar
datetime.time	net.razorvine.pickle.objects.Time
datetime.timedelta	net.razorvine.pickle.objects.TimeDelta
float	double (float isn't used)
array.array	array of appropriate primitive type (char, int, short, long, float, double)
list	java.util.List<Object>
tuple	Object[]
set	java.util.Set
dict	java.util.Map
bytes	byte[]
bytearray	byte[]
decimal	BigDecimal (except NaN which is mapped to Double.NaN)
custom class	Map<String, Object> (dict with class attributes including its name in "class")
Pyro4.core.URI	net.razorvine.pyro.PyroURI
Pyro4.core.Proxy	net.razorvine.pyro.PyroProxy
Pyro4.errors.*	net.razorvine.pyro.PyroException
Pyro4.utils.flame.FlameBuiltin	net.razorvine.pyro.FlameBuiltin
Pyro4.utils.flame.FlameModule	net.razorvine.pyro.FlameModule
Pyro4.utils.flame.RemoteInteractiveConsole	net.razorvine.pyro.FlameRemoteConsole

Java to Python (pickling)

JAVA	PYTHON
null	None
boolean	bool
byte	int
char	str/unicode (length 1)
String	str/unicode
double	float
float	float
int	int
short	int
BigDecimal	decimal
BigInteger	long
any array	array if elements are primitive type (else tuple)
Object[]	tuple (cannot contain self-references)
byte[]	bytearray
java.util.Date	datetime.datetime
java.util.Calendar	datetime.datetime
java.sql.Date	datetime.date
java.sql.Time	datetime.time
java.sql.Timestamp	datetime.datetime
Enum	the enum value as string
java.util.Set	set
Map, Hashtable	dict
Vector, Collection	list
Serializable	treated as a JavaBean, see below.
JavaBean	dict of the bean's public properties + `__class__` for the bean's type.
net.razorvine.pyro.PyroURI	Pyro4.core.URI
net.razorvine.pyro.PyroProxy	cannot be pickled.

Python to .NET (unpickling)

The unpickler simply returns an object. In the case of C#, that is a statically typed language so you will have to cast that to the appropriate type. Refer to this table to see what you can expect to receive. Tip: you can use the 'dynamic' type in some places to avoid excessive type casting.

PYTHON	.NET
None	null
bool	bool
int	int
long	long (c# doesn't have BigInteger so there's a limit on the size)
string	string
unicode	string
complex	Razorvine.Pickle.Objects.ComplexNumber
datetime.date	DateTime
datetime.datetime	DateTime
datetime.time	TimeSpan
datetime.timedelta	TimeSpan
float	double
array.array	array (all kinds of element types supported)
list	ArrayList (of objects)
tuple	object[]
set	HashSet<object>
dict	Hashtable (key=object, value=object)
bytes	ubyte[]
bytearray	ubyte[]
decimal	decimal (except NaN which is mapped to double.NaN)
custom class	IDictionary<string, object> (dict with class attributes including its name in "class")
Pyro4.core.URI	Razorvine.Pyro.PyroURI
Pyro4.core.Proxy	Razorvine.Pyro.PyroProxy
Pyro4.errors.*	Razorvine.Pyro.PyroException
Pyro4.utils.flame.FlameBuiltin	Razorvine.Pyro.FlameBuiltin
Pyro4.utils.flame.FlameModule	Razorvine.Pyro.FlameModule
Pyro4.utils.flame.RemoteInteractiveConsole	Razorvine.Pyro.FlameRemoteConsole

.NET to Python (pickling)

.NET	PYTHON
null	None
boolean	bool
byte	byte
sbyte	int
char	str/unicode (length 1)
string	str/unicode
double	float
float	float
int/short/sbyte	int
uint/ushort/byte	int
decimal	decimal
byte[]	bytearray
primitivetype[]	array
object[]	tuple (cannot contain self-references)
DateTime	datetime.datetime
TimeSpan	datetime.timedelta
Enum	just the enum value as string
HashSet	set
Map, Hashtable	dict
Collection	list
Enumerable	list
object with public properties	dictionary of those properties + class
anonymous class type	dictonary of the public properties
Razorvine.Pyro.PyroURI	Pyro4.core.URI
Razorvine.Pyro.PyroProxy	cannot be pickled.