PRELIMINARY
CONCEPT
python
DESCRIPTION
Python can be used to extend the LDMud driver. At the startup
of LDMud a python script will be called that can register
additional efuns. The python script can either be given
on the command line using the --python-script option,
or at compile time with the --with-python-script configuration
option.
The python script can import the builtin ldmud module for
extending LDMud and accessing LDMud information.
STARTUP SCRIPT
The startup script can be a single Python script file. This script
is executed as the main routine (i.e. __name__ == '__main__') when
ldmud starts and before the master object is loaded.
It's also possible to specify a package with a __main__ module
(currently this may be a directory or a zip file). In this case
the __main__ submodule will be executed at startup. The package
itself will be placed into sys.path, so additional content can
be imported.
LDMUD MODULE
The ldmud module is only available for Python programs executed
inside the ldmud process and provides the following functions:
- register_efun(name, function) -> None
Registers a new efun name. This is not allowed during
compilation of an LPC object.
If the Python function has type annotations for its
arguments and return value, the type is checked
at compile and runtime. Union types can be specified
as tuples of types.
- unregister_efun(name) -> None
Removes a python efun from registration. This is not
allowed during compilation of an LPC object. The
removal will only affect newly compiled code,
already compiled code will produce errors when
calling this efun.
- register_type(name, class) -> None
Registers a type for use in LPC. This is not allowed
during compilation of an LPC object.
The type name will then be regarded as a reserved word
when compiling LPC code and can be used as a regular
LPC type. To actually create objects of the types,
additional registration of corresponding efuns is needed.
For details about the usage, see PYTHON TYPES below.
- unregister_type(name) -> None
Removes a python type from registration. This is not
allowed during compilation of an LPC object. The removal
will only affect newly compiled code. Already compiled
code will still work afterwards.
- register_socket(fd, function [,eventmask]) -> None
Registers a socket <fd> to watch for events (like
poll/select). The socket must be either given as
an integer or an object with a fileno() method
returning an integer. The function must be a callable
accepting one argument, the actual event mask.
<eventmask> may be an combination of select.POLLIN,
select.POLLOUT and select.POLLPRI or a callable
returning such a combination.
- unregister_socket(fd) -> None
Removes a previously registered socket from the
watch list.
- register_hook(hook, function) -> None
Register a hook. The python function will be called
whenever <hook> happens. <hook> can be one of the
following:
ON_HEARTBEAT
Called without arguments for every backend loop
ON_OBJECT_CREATED
Called whenever an object was created, with the
object as its first and only argument. This call
happens before any LPC code of the object ran.
ON_OBJECT_DESTRUCTED
Called just before an object will be destructed,
with the object as its first and only argument.
ON_CHILD_PROCESS_TERMINATED
Called without any arguments whenever a SIGCHLD signal
was received. This could also happen for processes
spawned by the driver itself (eg. erq).
ON_SIGINT
Called without any argument whenever a SIGINT signal
was received. (This is just informative, the driver
will execute the DC_SIGACTION_SIGINT action also.)
ON_SIGTERM
Called without any argument whenever a SIGTERM signal
was received. The driver will terminate afterwards.
ON_SIGHUP
Called without any argument whenever a SIGHUP signal
was received. (This is just informative, the driver
will execute the DC_SIGACTION_SIGHUP action also.)
ON_SIGUSR1
Called without any argument whenever a SIGUSR1 signal
was received. (This is just informative, the driver
will execute the DC_SIGACTION_SIGUSR1 action also.)
ON_SIGUSR2
Called without any argument whenever a SIGUSR2 signal
was received. (This is just informative, the driver
will execute the DC_SIGACTION_SIGUSR2 action also.)
- unregister_hook(hook, function) -> None
Removes a hook function.
- get_master() - > Object
Returns the current master object.
Returns None, if there is no master object (yet).
- get_simul_efun() - > Object
Returns the current simul-efun object
(or None if there is none).
This module provides the following types:
- Object(filename)
Corresponds to the LPC object type.
On instantiation a filename for an object
to search or load is required.
Has the following members:
name
The object name
functions
Contains all the visible functions (private functions
are excluded) as attributes. They support the call
operator and contain the following attributes:
name
The name of the function
file_name
The file that contains the function's definition
line_number
The starting line number of the function's definition
arguments
A list of all arguments with their type, flags
(combination of LA_* constants) and position.
return_type
The return type as Python object (maybe missing if
unknown or mixed).
flags
A combination of the following flags:
LF_STATIC, LF_NOMASK, LF_VARARGS, LF_VIRTUAL and
LF_DEPRECATED
visibility:
One of the following:
VIS_PRIVATE, VIS_PROTECTED, VIS_VISIBLE, VIS_PUBLIC
variables
Contains all variables as attributes. They contain the
following attributes:
name
The name of the variable
value
The value of the variable. This attribute is writable
to assign a new value.
type
The type as a Python object (maybe missing if
unknown or mixed).
flags
A combination of the following flags:
VF_NOSAVE, VF_NOMASK, VF_VIRTUAL and VF_DEPRECATED
visibility:
One of the following:
VIS_PRIVATE, VIS_PROTECTED, VIS_VISIBLE, VIS_PUBLIC
For type checks the type object can be subscripted with a
filename to create a named object type: Object["/name"]
- LWObject(filename)
Corresponds to the LPC lwobject type.
On instantiation a filename of a blueprint to create
a lightweight object from is required.
Has the following members:
program_name
The program name (file name it was created from)
functions
Contains all the visible functions (private functions
are excluded) as attributes. They are similar to the
same member of the Object type.
variables
Contains all variables as attributes. They are similar
to the same member of the Object type.
For type checks the type object can be subscripted with a
filename to create a named lwobject type: LWObject["/name"]
- Array([values | size])
Corresponds to an LPC array.
Can either be initialized with a list of values
or to a given size.
Supports element access with [], len() and __contains__.
For type checks the type object can be subscripted with an
element type to create a concrete array type: Array[Mapping]
- Mapping([values | width])
Corresponds to an LPC mapping.
Can either be initialized with a dict, a list of tuples
or as an empty mapping with a given width.
Supports element access with [], len(), __contains__
and has a width member.
- Struct(object, name [, values])
Corresponds to an LPC struct.
On initialization the name of the struct definition and
the correspopnding object is required. It can be initialized
with a list of values or dict.
Has the following members:
name
The name of the struct
program_name
The name of the program that defined the struct.
members
Contains all members as attributes. They contain the
following attributes:
name
The name of the member
value
The value of the member. This attribute is writable
to assign a new value.
type
The type as a Python object (maybe missing if
unknown or mixed).
For type checks the type object can be subscripted to create
a specific struct type: Struct[program, name], whereas the
program can be given as a file name or object. When using this
for creating a struct, only values need to be passed.
- Closure(object [,name [, lfun_object]])
Corresponds to an LPC closure.
On initialization a closure bound to <object> will be created,
like a call to symbol_function(<name> [, <lfun_object>]).
Supports function calls.
- Coroutine()
Corresponds to an LPC coroutine.
They can only be created by LPC code and are not compatible
with Python coroutines.
Supports function calls and has the following members:
object
The object the coroutine belongs to.
program_name
The name of the program that defined the coroutine.
function_name
The name of the function that defined the coroutine.
file_name
The name of the file that contains the definition.
line_number
The current line where the coroutine is suspended.
variables
Contains all local variables as attributes with
their current value.
- Symbol(name [, quotes])
Corresponds to an LPC symbol.
On initialization the name of the symbol is required.
Optionally the number of quotes (at least 1) can be specified.
Has two members: name and quotes.
- QuotedArray(array [, quotes])
Corresponds to an LPC quoted array.
On initialization an array is required.
Optionally the number of quotes (at least 1) can be specified.
Has two members: array and quotes.
- Lvalue(value)
Creates an lvalue reference for the given value.
Has two member: value and members.
If the value is an array, mapping or string, then lvalues
to its elements can be created with [].
If the value is a struct, then lvalues to its members can
be created with the members attribute. It contains all
the struct members as attributes and will return an Lvalue
object to the struct member.
- LPCType(type)
Corresponds to an LPC lpctype value. For basic types this
is a no-op and returns the basic type. This type will provide
the corresponding LDMud type object for basic python types,
and it can be used to construct a union type by passing a
tuple of types.
A union type allows iteration over its basic types and
supports __contains__.
- Integer, Float, String, Bytes
These are derived types from Python's int, float, str and
bytes. They offer the | (or) operator to create union of
types.
This module contains the following sub-namespaces:
- efuns
This namespace contains all original efuns (without any
registered python efuns or simul-efuns). These can be called
as a regular function.
There is mapping of LPC values to Python values for the following types:
int <-> int(, bool)
float <-> float
string <-> str
bytes <-> bytes
Type definitions are translated in a similar fashion, additionally the
following mappings are done:
void <-> None
union <-> tuple of types
PYTHON TYPES
Without any special functions Python types are treated opaque in LPC.
There is no introspection available, beside what get_type_info()
returns, and there is no facility to create those in LPC. Python
objects need to be created and processed by a registered Python efun.
But those types can be extended with special functions to make them
more usable in LPC.
Regular LPC operations can be applied to those python objects and
will call the corresponding special member functions. If those
member functions are not available, the corresponding LPC operations
aren't either. For compile time type checking those special member
functions can have type annotations just like efun functions.
The following operations are supported:
+, -, *, /, %, <<, >>, &, |, ^, >, >=, ==, !=, <, <=.
For each operation the lhs function (i.e. __add__), the rhs function
(i.e. __radd__), and the assignment function (i.e. __iadd__) is
supported. The rhs function is also supported for the comparison
operations (i.e. __rlt__, this is a non-standard extension to the
Python functions).
Python objects can also extend regular efuns. When the first argument
to an efun is a Python object, a function named __efun_<name>__ is
called in the Python object instead (when available). The function
must accept the same number of arguments as the original efun. (And
there must not be a registered Python efun of the same name.)
Additionally a Python type can implement the following support
functions for LPC efuns:
__repr__
Used by sprintf() for printing a Python object.
Should return a string.
__copy__
Used by copy() and deep_copy() for copying a Python object.
(Deep copying a Python object is currently not supported.)
Should return a Python object of the same type.
__save__
Used by save_value()/save_object() to save a Python object.
Should return an LPC type (e.g. a string).
__restore__
Used by restore_value()/restore_object() to restore a Python
object. This should be a static method that gets the value
from __save__ as the only argument and will return the
restored object.
EXAMPLE
import ldmud
def hello_world(name: str) -> int:
print("Hello, world, %s!\n" % (name,))
return 1
ldmud.register_efun("hello", hello_world)
NOTES
Just like simul-efuns python efuns can shadow real efuns. The
original efun is then inaccessible for LPC code (except for code
that was compiled before the efun was registered). Python efuns are
nearly indistinguishable from real efuns, they also use the efun::
prefix. However they can be detected with
CLOSURE_IS_PYTHON_EFUN(get_type_info(#'efun,1))
Without the prefix the order of name resolution for function calls is:
1. lfuns
2. simul-efuns
3. python efuns
4. real efuns
Also just like simul-efuns python-registered efuns are called
from LPC code that was compiled after the registration. LPC code
that was compiled before the registration will still call the
original efuns (or throw a compile error if that efun doesn't exist).
Therefore such efuns should be registered in the python startup
script.
When a python efun is unregistered, code that was compiled while the
registration was in effect will throw a runtime error. (Regardless
of whether a driver efun with the same name exists or not.)
There is a limit of 2048 python efuns. Not only registered, but also
formerly registered - but now unregistered - efuns count toward that
limit. Re-registering the same efun name again won't count a second
time. (LPC code that was compiled during the previous registration
will also call the new efun after the re-registration.)
As LDMud is single-threaded, the python code will run in the same
thread as the LPC machine. So any long-running python function will
halt the MUD for all players. Hence python functions should return
promptly and source out any lengthy tasks to another process. If
other threads are spawned from python, then these threads are not
allowed to access any LDMud functions or objects.
Finally a note of caution: Don't change the meaning of base efuns
fundamentally as it furthers confusion and hinders exchange of LPC
code and knowledge between mudlibs.
HISTORY
LDMud 3.5 implemented the python functionality.
LDMud 3.6 added type checks.
SEE ALSO
simul_efun(C)