Lazy and Self-destructive Python Tools (cyclus.lazyasd)

Lazy and self destructive containers for speeding up module import.

class cyclus.lazyasd.BackgroundModuleLoader(name, package, replacements, *args, **kwargs)

Thread to load modules in the background.


A boolean value indicating whether this thread is a daemon thread.

This must be set before start() is called, otherwise RuntimeError is raised. Its initial value is inherited from the creating thread; the main thread is not a daemon thread and therefore all threads created in the main thread default to daemon = False.

The entire Python program exits when no alive non-daemon threads are left.


Thread identifier of this thread or None if it has not been started.

This is a nonzero integer. See the thread.get_ident() function. Thread identifiers may be recycled when a thread exits and another thread is created. The identifier is available even after the thread has exited.


Return whether the thread is alive.

This method returns True just before the run() method starts until just after the run() method terminates. The module function enumerate() returns a list of all alive threads.


Return whether the thread is alive.

This method returns True just before the run() method starts until just after the run() method terminates. The module function enumerate() returns a list of all alive threads.


Wait until the thread terminates.

This blocks the calling thread until the thread whose join() method is called terminates – either normally or through an unhandled exception or until the optional timeout occurs.

When the timeout argument is present and not None, it should be a floating point number specifying a timeout for the operation in seconds (or fractions thereof). As join() always returns None, you must call isAlive() after join() to decide whether a timeout happened – if the thread is still alive, the join() call timed out.

When the timeout argument is not present or None, the operation will block until the thread terminates.

A thread can be join()ed many times.

join() raises a RuntimeError if an attempt is made to join the current thread as that would cause a deadlock. It is also an error to join() a thread before it has been started and attempts to do so raises the same exception.


A string used for identification purposes only.

It has no semantics. Multiple threads may be given the same name. The initial name is set by the constructor.


Start the thread’s activity.

It must be called at most once per thread object. It arranges for the object’s run() method to be invoked in a separate thread of control.

This method will raise a RuntimeError if called more than once on the same thread object.

class cyclus.lazyasd.BackgroundModuleProxy(modname)

Proxy object for modules loaded in the background that block attribute access until the module is loaded..

class cyclus.lazyasd.LazyBool(load, ctx, name)
class cyclus.lazyasd.LazyDict(loaders, ctx, name)
clear() → None. Remove all items from D.
get(k[, d]) → D[k] if k in D, else d. d defaults to None.
items() → a set-like object providing a view on D's items
keys() → a set-like object providing a view on D's keys
pop(k[, d]) → v, remove specified key and return the corresponding value.

If key is not found, d is returned if given, otherwise KeyError is raised.

popitem() → (k, v), remove and return some (key, value) pair

as a 2-tuple; but raise KeyError if D is empty.

setdefault(k[, d]) → D.get(k,d), also set D[k]=d if k not in D
update([E, ]**F) → None. Update D from mapping/iterable E and F.

If E present and has a .keys() method, does: for k in E: D[k] = E[k] If E present and lacks .keys() method, does: for (k, v) in E: D[k] = v In either case, this is followed by: for k, v in F.items(): D[k] = v

values() → an object providing a view on D's values
class cyclus.lazyasd.LazyObject(load, ctx, name)

Decorator for constructing lazy booleans from a function.


Decorator for constructing lazy dicts from a function.


Decorator for constructing lazy objects from a function.

cyclus.lazyasd.load_module_in_background(name, package=None, debug='DEBUG', env=None, replacements=None)

Entry point for loading modules in background thread.


name : str

Module name to load in background thread.

package : str or None, optional

Package name, has the same meaning as in importlib.import_module().

debug : str, optional

Debugging symbol name to look up in the environment.

env : Mapping or None, optional

Environment this will default to __xonsh_env__, if available, and os.environ otherwise.

replacements : Mapping or None, optional

Dictionary mapping fully qualified module names (eg that import the lazily loaded moudle, with the variable name in that module. For example, suppose that imports module a as b, this dict is then {‘’: ‘b’}.


module : ModuleType

This is either the original module that is found in sys.modules or a proxy module that will block until delay attribute access until the module is fully loaded.