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# xonsh.lib.lazyasd

Lazy and self destructive containers for speeding up module import.

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

  Thread to load modules in the background.

  This constructor should always be called with keyword arguments. Arguments are:

  group should be None; reserved for future extension when a ThreadGroup class is implemented.

  target is the callable object to be invoked by the run() method. Defaults to None, meaning nothing is called.

  name is the thread name. By default, a unique name is constructed of the form “Thread-N” where N is a small decimal number.

  args is a list or tuple of arguments for the target invocation. Defaults to ().

  kwargs is a dictionary of keyword arguments for the target invocation. Defaults to {}.

  context is the contextvars.Context value to use for the thread. The default value is None, which means to check sys.flags.thread_inherit_context. If that flag is true, use a copy of the context of the caller. If false, use an empty context. To explicitly start with an empty context, pass a new instance of contextvars.Context(). To explicitly start with a copy of the current context, pass the value from contextvars.copy_context().

  If a subclass overrides the constructor, it must make sure to invoke the base class constructor (Thread.__init__()) before doing anything else to the thread.

  getName()

    Return a string used for identification purposes only.

    This method is deprecated, use the name attribute instead.

  isDaemon()

    Return whether this thread is a daemon.

    This method is deprecated, use the daemon attribute instead.

  is_alive()

    Return whether the thread is alive.

    This method returns True just before the run() method starts until just after the run() method terminates. See also the module function enumerate().

  join(timeout=None)

    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 is_alive() 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.

  run()

    Method representing the thread’s activity.

    You may override this method in a subclass. The standard run() method invokes the callable object passed to the object’s constructor as the target argument, if any, with sequential and keyword arguments taken from the args and kwargs arguments, respectively.

  setDaemon(daemonic)

    Set whether this thread is a daemon.

    This method is deprecated, use the .daemon property instead.

  setName(name)

    Set the name string for this thread.

    This method is deprecated, use the name attribute instead.

  start()

    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.

  property daemon

    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 only daemon threads are left.

  property ident

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

    This is a nonzero integer. See the 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.

  property name

    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.

  property native_id

    Native integral thread ID of this thread, or None if it has not been started.

    This is a non-negative integer. See the get_native_id() function. This represents the Thread ID as reported by the kernel.

class xonsh.lib.lazyasd.BackgroundModuleProxy(modname)

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

class xonsh.lib.lazyasd.LazyBool(load, ctx, name)

  Boolean like object that lazily computes it boolean value when it is first asked. Once loaded, this result will replace itself in the provided context (typically the globals of the call site) with the given name.

  For example, you can prevent the complex boolean until it is actually used:

      ALIVE = LazyDict(lambda: not DEAD, globals(), 'ALIVE')

  Parameters:
    load function with no arguments

      A loader function that performs the actual boolean evaluation.

    ctx Mapping

      Context to replace the LazyBool instance in with the the fully loaded mapping.

    name str

      Name in the context to give the loaded mapping. This should be the name on the LHS of the assignment.

class xonsh.lib.lazyasd.LazyDict(loaders, ctx, name)

  Dictionary like object that lazily loads its values from an initial dict of key-loader function pairs. Each key is loaded when its value is first accessed. Once fully loaded, this object will replace itself in the provided context (typically the globals of the call site) with the given name.

  For example, you can prevent the compilation of a bunch of regular expressions until they are actually used:

      RES = LazyDict({
              'dot': lambda: re.compile('.'),
              'all': lambda: re.compile('.*'),
              'two': lambda: re.compile('..'),
              }, globals(), 'RES')

  Parameters:
    loaders Mapping of keys to functions with no arguments

      A mapping of loader function that performs the actual value construction upon access.

    ctx Mapping

      Context to replace the LazyDict instance in with the the fully loaded mapping.

    name str

      Name in the context to give the loaded mapping. This should be the name on the LHS of the assignment.

  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.keys(): 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 xonsh.lib.lazyasd.LazyObject(load, ctx, name)

  Lazily loads an object via the load function the first time an attribute is accessed. Once loaded it will replace itself in the provided context (typically the globals of the call site) with the given name.

  For example, you can prevent the compilation of a regular expression until it is actually used:

      DOT = LazyObject((lambda: re.compile('.')), globals(), 'DOT')

  Parameters:
    load function with no arguments

      A loader function that performs the actual object construction.

    ctx Mapping

      Context to replace the LazyObject instance in with the object returned by load().

    name str

      Name in the context to give the loaded object. This should be the name on the LHS of the assignment.

xonsh.lib.lazyasd.lazybool(f)

  Decorator for constructing lazy booleans from a function.

xonsh.lib.lazyasd.lazydict(f)

  Decorator for constructing lazy dicts from a function.

xonsh.lib.lazyasd.lazyobject(f: Callable[[...], RT]) → RT

  Decorator for constructing lazy objects from a function.

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

  Entry point for loading modules in background thread.

  Parameters:
    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 foo.bar.baz) that import the lazily loaded module, with the variable name in that module. For example, suppose that foo.bar imports module a as b, this dict is then {‘foo.bar’: ‘b’}.

  Returns:
    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.