PyStoreObj Class Reference

a (simplified) python wrapper for StoreObjPtr. More...

#include <PyStoreObj.h>

Collaboration diagram for PyStoreObj:

Public Member Functions
	PyStoreObj (const std::string &name, DataStore::EDurability durability=DataStore::EDurability::c_Event)
	constructor.
	PyStoreObj (TClass *objClass, DataStore::EDurability durability=DataStore::EDurability::c_Event)
	constructor.
	PyStoreObj (TClass *objClass, const std::string &name, DataStore::EDurability durability=DataStore::EDurability::c_Event)
	constructor.
bool	registerInDataStore (DataStore::EStoreFlags storeFlags)
	Register the object in the DataStore.
bool	registerInDataStore (const std::string &name="", DataStore::EStoreFlags storeFlags=DataStore::EStoreFlags::c_WriteOut)
	Register the object in the DataStore.
bool	isRequired (const std::string &name="")
	Ensure this object has been registered previously.
bool	isOptional (const std::string &name="")
	Tell the DataStore about an optional input.
bool	hasValidClass () const
	Check whether a TClass for the contained object could be determined.
bool	isValid () const
	Check whether the object was registered and created.
	operator bool () const
	Does this PyStoreObj contain a valid datastore object?
TObject *	obj () const
	Returns the attached DataStore object, or nullptr if no valid object exists.
TObject *	operator-> () const
	Returns the attached DataStore object, or nullptr if no valid object exists.
bool	assign (TObject *object, bool replace=false)
	Assign 'object' to the accessor.
bool	create (bool replace=false)
	Create default constructed object in the DataStore.

Static Public Member Functions
static std::vector< std::string >	list (DataStore::EDurability durability=DataStore::EDurability::c_Event)
	Return list of available objects for given durability.
static void	printList (DataStore::EDurability durability=DataStore::EDurability::c_Event)
	Print list of available objects for given durability.

Private Member Functions
void	ensureAttached () const
	Ensure that contained TObject has been attached to a memory location on the DataStore.
void	attach () const
	Lookup the store entry and cache a pointer to it.

Private Attributes
StoreAccessorBase	m_storeAccessor
	Store accessor to retrieve the object.
StoreEntry *	m_storeEntry = nullptr
	Pointer to the DataStore entry - serves as an internal cache omitting repeated look up from the DataStore.

Detailed Description

a (simplified) python wrapper for StoreObjPtr.

Compared to StoreObjPtr, PyStoreObj returns only TObjects (since it doesn't use templates). Thanks to Python, you can still access all public functions and data members of the actual type.

You can check the runtime type information of the returned objects by using Python's built-in type() function.

Usage example

Inside a Python module's event() function, you can access DataStore objects like this:

from ROOT import Belle2
evtmetadata = Belle2.PyStoreObj('EventMetaData')
# Alternatively: evtmetadata = Belle2.PyStoreObj(Belle2.EventMetaData.Class())
if not evtmetadata:
  B2ERROR("No EventMetaData found");
else:
  event = evtmetadata.getEvent()
  # alternatively: evtmetadata.obj().getEvent()

Most of the time you can just use the PyStoreObj instance like an instance of the class it represents, i.e. call all the members. The only exceptions are if the class has members which are also present in PyStoreObj (for example isValid() or isRequired()). In this case you need to use the obj() member to obtain a reference to the real object first as shown in the example.

Creating objects

You can also create new objects in your Python basf2 module, using registerInDataStore() and create(). Since you cannot specify the type directly, as with template arguments to StoreObjPtr, the class name is assumed to be identical to the 'name' argument given to the constructor, and to reside in the Belle2 namespace. Consequently, you can only create objects with their default names.

See display/examples/displaydata.py for a concrete example.

See also

PyStoreArray and the Conditions Data interface classes PyDBObj and PyDBArray

Definition at line 67 of file PyStoreObj.h.

Constructor & Destructor Documentation

PyStoreObj() [1/3]

PyStoreObj ( const std::string &  name, DataStore::EDurability  durability = DataStore::EDurability::c_Event  )

explicit

constructor.

Parameters

name	Name of the entry to be accessed
durability	0: event, 1: persistent

Definition at line 40 of file PyStoreObj.cc.

                                                       :
  PyStoreObj(replaceNullPtr(DataStore::getTClassFromDefaultObjectName(name),
                            TObject::Class()),
             /* Default to TObject for unknown class for backwards compatability */
             name,
             durability)
{
}

PyStoreObj() [2/3]

PyStoreObj ( TClass *  objClass, DataStore::EDurability  durability = DataStore::EDurability::c_Event  )

explicit

constructor.

Parameters

objClass	Class of the object to be accessed
durability	0: event, 1: persistent

Definition at line 50 of file PyStoreObj.cc.

                                                        :
  PyStoreObj(objClass, DataStore::defaultObjectName(objClass), durability)
{
}

PyStoreObj() [3/3]

PyStoreObj ( TClass *  objClass, const std::string &  name, DataStore::EDurability  durability = DataStore::EDurability::c_Event  )

explicit

constructor.

Parameters

objClass	Class of the object to be accessed
name	Name of the entry to be accessed
durability	0: event, 1: persistent

Definition at line 56 of file PyStoreObj.cc.

                                                        :
  m_storeAccessor(name, durability, objClass, false)
{
  // Attach if already created
  attach();
}

Member Function Documentation

assign()

bool assign	(	TObject *	object,
		bool	replace = false
	)

Assign 'object' to the accessor.

(takes ownership).

Parameters

object	The object that should be put in the DataStore, should be of same type as the one used by this accessor.
replace	Should an existing object be replaced? (if existing and supplied object are equal, this has no effect)

Returns

True if the assignment succeeded. If false, assign() will delete 'object', do not use it afterwards.

Definition at line 140 of file PyStoreObj.cc.

{
  return m_storeAccessor.assign(object, replace);
}

attach()

void attach ( ) const

private

Lookup the store entry and cache a pointer to it.

Definition at line 135 of file PyStoreObj.cc.

{
  m_storeEntry = DataStore::Instance().getEntry(m_storeAccessor);
}

create()

bool create

(

bool

replace = false

)

Create default constructed object in the DataStore.

Parameters

replace

Should an existing object be replaced?

Returns

True if the creation succeeded.

Definition at line 103 of file PyStoreObj.cc.

{
  ensureAttached();
  if (not m_storeEntry) {
    // Attaching failed
    B2ERROR("Cannot create unregistered PyStoreObj.");
    return false;
  }
 
  // Short cut when an object has been created and no replacement is requested.
  if (isValid() and not replace) return true;
 
  if (not isValid() and not hasValidClass()) {
    B2ERROR("Cannot create PyStoreObj with unknown TClass.");
    return false;
  } else {
    // StoreObj has been created before or has a valid class
    // Go ahead and (re)create it
    return m_storeAccessor.create(replace);
  }
}

ensureAttached()

void ensureAttached ( ) const

private

Ensure that contained TObject has been attached to a memory location on the DataStore.

Definition at line 125 of file PyStoreObj.cc.

{
  if (not m_storeEntry) {
    attach();
    if (not m_storeEntry) {
      B2ERROR("PyStoreObj " << m_storeAccessor.readableName() << " has not been registered!");
    }
  }
}

hasValidClass()

bool hasValidClass

(

)

const

Check whether a TClass for the contained object could be determined.

Definition at line 97 of file PyStoreObj.cc.

{
  const TClass* objClass = m_storeAccessor.getClass();
  return objClass and objClass != TObject::Class();
}

isOptional()

bool isOptional

(

const std::string &

name = ""

)

Tell the DataStore about an optional input.

Mainly useful for creating diagrams of module inputs and outputs. This must be called in the initialization phase.

Parameters

name	If not empty, use non-default name for this object.

Returns

True if the object exists.

Definition at line 87 of file PyStoreObj.cc.

{
  return m_storeAccessor.isOptional(name);
}

isRequired()

bool isRequired

(

const std::string &

name = ""

)

Ensure this object has been registered previously.

Will cause an ERROR if it does not exist. This must be called in the initialization phase.

Parameters

name	If not empty, use non-default name for this object.

Returns

True if the object exists.

Definition at line 82 of file PyStoreObj.cc.

{
  return m_storeAccessor.isRequired(name);
}

isValid()

bool isValid

(

)

const

Check whether the object was registered and created.

Definition at line 92 of file PyStoreObj.cc.

{
  return m_storeEntry and m_storeEntry->ptr;
}

list()

vector< string > list ( DataStore::EDurability  durability = DataStore::EDurability::c_Event )

static

Return list of available objects for given durability.

Definition at line 28 of file PyStoreObj.cc.

{
  return DataStore::Instance().getListOfObjects(TObject::Class(), durability);
}

obj()

TObject * obj ( ) const

inline

Returns the attached DataStore object, or nullptr if no valid object exists.

Definition at line 148 of file PyStoreObj.h.

{ ensureAttached(); return isValid() ? m_storeEntry->ptr : nullptr; }

operator bool()

operator bool ( ) const

inline

Does this PyStoreObj contain a valid datastore object?

Accessing the object's data is UNSAFE if this returns false.

Definition at line 145 of file PyStoreObj.h.

{ return isValid(); }

operator->()

TObject * operator-> ( ) const

inline

Returns the attached DataStore object, or nullptr if no valid object exists.

Definition at line 151 of file PyStoreObj.h.

{ return obj(); }

printList()

void printList ( DataStore::EDurability  durability = DataStore::EDurability::c_Event )

static

Print list of available objects for given durability.

Definition at line 33 of file PyStoreObj.cc.

{
  for (const auto& n : list(durability))
    B2INFO(n);
}

registerInDataStore() [1/2]

bool registerInDataStore	(	const std::string &	name = "",
		DataStore::EStoreFlags	storeFlags = DataStore::EStoreFlags::c_WriteOut
	)

Register the object in the DataStore.

This must be called in the initialization phase, and a TClass or name=class name must have been supplied during construction.

Parameters

name	Name of the entry to be registered. Empty for default name.
storeFlags	ORed combination of DataStore::EStoreFlags. (default: c_WriteOut)

Returns

True if the registration succeeded.

Definition at line 70 of file PyStoreObj.cc.

{
  if (not hasValidClass()) {
    B2ERROR("Cannot register PyStoreObj '" << name << "' with unknown TClass. Please supply one to the PyStoreObj constructor.");
    return false;
  }
 
  bool success = m_storeAccessor.registerInDataStore(name, storeFlags);
  if (success) attach();
  return success;
}

registerInDataStore() [2/2]

bool registerInDataStore

(

DataStore::EStoreFlags

storeFlags

)

Register the object in the DataStore.

This must be called in the initialization phase.

Parameters

storeFlags

ORed combination of DataStore::EStoreFlags. (default: c_WriteOut)

Returns

True if the registration succeeded.

Definition at line 65 of file PyStoreObj.cc.

{
  return registerInDataStore(m_storeAccessor.getName(), storeFlags);
}

Member Data Documentation

m_storeAccessor

StoreAccessorBase m_storeAccessor

private

Store accessor to retrieve the object.

Definition at line 178 of file PyStoreObj.h.

m_storeEntry

StoreEntry* m_storeEntry = nullptr

mutableprivate

Pointer to the DataStore entry - serves as an internal cache omitting repeated look up from the DataStore.

Definition at line 181 of file PyStoreObj.h.

---

The documentation for this class was generated from the following files:

• framework/pybasf2/include/PyStoreObj.h
• framework/pybasf2/src/PyStoreObj.cc