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# This file is part of daf_butler. 

# 

# Developed for the LSST Data Management System. 

# This product includes software developed by the LSST Project 

# (http://www.lsst.org). 

# See the COPYRIGHT file at the top-level directory of this distribution 

# for details of code ownership. 

# 

# This program is free software: you can redistribute it and/or modify 

# it under the terms of the GNU General Public License as published by 

# the Free Software Foundation, either version 3 of the License, or 

# (at your option) any later version. 

# 

# This program is distributed in the hope that it will be useful, 

# but WITHOUT ANY WARRANTY; without even the implied warranty of 

# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 

# GNU General Public License for more details. 

# 

# You should have received a copy of the GNU General Public License 

# along with this program. If not, see <http://www.gnu.org/licenses/>. 

 

__all__ = ("iterable", "allSlots", "slotValuesAreEqual", "slotValuesToHash", 

"getFullTypeName", "getInstanceOf", "Singleton", "transactional", 

"getObjectSize", "stripIfNotNone", "PrivateConstructorMeta") 

 

import sys 

import functools 

 

from lsst.utils import doImport 

 

 

def iterable(a): 

"""Make input iterable. 

 

There are three cases, when the input is: 

 

- iterable, but not a `str` -> iterate over elements 

(e.g. ``[i for i in a]``) 

- a `str` -> return single element iterable (e.g. ``[a]``) 

- not iterable -> return single elment iterable (e.g. ``[a]``). 

 

Parameters 

---------- 

a : iterable or `str` or not iterable 

Argument to be converted to an iterable. 

 

Returns 

------- 

i : `generator` 

Iterable version of the input value. 

""" 

if isinstance(a, str): 

yield a 

return 

try: 

yield from a 

except Exception: 

yield a 

 

 

def allSlots(self): 

""" 

Return combined ``__slots__`` for all classes in objects mro. 

 

Parameters 

---------- 

self : `object` 

Instance to be inspected. 

 

Returns 

------- 

slots : `itertools.chain` 

All the slots as an iterable. 

""" 

from itertools import chain 

return chain.from_iterable(getattr(cls, "__slots__", []) for cls in self.__class__.__mro__) 

 

 

def slotValuesAreEqual(self, other): 

""" 

Test for equality by the contents of all slots, including those of its 

parents. 

 

Parameters 

---------- 

self : `object` 

Reference instance. 

other : `object` 

Comparison instance. 

 

Returns 

------- 

equal : `bool` 

Returns True if all the slots are equal in both arguments. 

""" 

return all((getattr(self, slot) == getattr(other, slot) for slot in allSlots(self))) 

 

 

def slotValuesToHash(self): 

""" 

Generate a hash from slot values. 

 

Parameters 

---------- 

self : `object` 

Instance to be hashed. 

 

Returns 

------- 

h : `int` 

Hashed value generated from the slot values. 

""" 

return hash(tuple(getattr(self, slot) for slot in allSlots(self))) 

 

 

def getFullTypeName(cls): 

"""Return full type name of the supplied entity. 

 

Parameters 

---------- 

cls : `type` or `object` 

Entity from which to obtain the full name. Can be an instance 

or a `type`. 

 

Returns 

------- 

name : `str` 

Full name of type. 

""" 

# If we have an instance we need to convert to a type 

131 ↛ 132line 131 didn't jump to line 132, because the condition on line 131 was never true if not hasattr(cls, "__qualname__"): 

cls = type(cls) 

return cls.__module__ + "." + cls.__qualname__ 

 

 

def getInstanceOf(typeOrName): 

"""Given the type name or a type, instantiate an object of that type. 

 

If a type name is given, an attempt will be made to import the type. 

 

Parameters 

---------- 

typeOrName : `str` or Python class 

A string describing the Python class to load or a Python type. 

""" 

if isinstance(typeOrName, str): 

cls = doImport(typeOrName) 

else: 

cls = typeOrName 

return cls() 

 

 

class Singleton(type): 

"""Metaclass to convert a class to a Singleton. 

 

If this metaclass is used the constructor for the singleton class must 

take no arguments. This is because a singleton class will only accept 

the arguments the first time an instance is instantiated. 

Therefore since you do not know if the constructor has been called yet it 

is safer to always call it with no arguments and then call a method to 

adjust state of the singleton. 

""" 

 

_instances = {} 

 

def __call__(cls): # noqa N805 

if cls not in cls._instances: 

cls._instances[cls] = super(Singleton, cls).__call__() 

return cls._instances[cls] 

 

 

def transactional(func): 

"""Decorator that wraps a method and makes it transactional. 

 

This depends on the class also defining a `transaction` method 

that takes no arguments and acts as a context manager. 

""" 

@functools.wraps(func) 

def inner(self, *args, **kwargs): 

with self.transaction(): 

return func(self, *args, **kwargs) 

return inner 

 

 

def getObjectSize(obj, seen=None): 

"""Recursively finds size of objects. 

 

Only works well for pure python objects. For example it does not work for 

``Exposure`` objects where all the content is behind getter methods. 

 

Parameters 

---------- 

obj : `object` 

Instance for which size is to be calculated. 

seen : `set`, optional 

Used internally to keep track of objects already sized during 

recursion. 

 

Returns 

------- 

size : `int` 

Size in bytes. 

 

See Also 

-------- 

sys.getsizeof 

 

Notes 

----- 

See https://goshippo.com/blog/measure-real-size-any-python-object/ 

""" 

size = sys.getsizeof(obj) 

if seen is None: 

seen = set() 

obj_id = id(obj) 

if obj_id in seen: 

return 0 

# Important mark as seen *before* entering recursion to gracefully handle 

# self-referential objects 

seen.add(obj_id) 

if isinstance(obj, dict): 

size += sum([getObjectSize(v, seen) for v in obj.values()]) 

size += sum([getObjectSize(k, seen) for k in obj.keys()]) 

elif hasattr(obj, "__dict__"): 

size += getObjectSize(obj.__dict__, seen) 

elif hasattr(obj, "__iter__") and not isinstance(obj, (str, bytes, bytearray)): 

size += sum([getObjectSize(i, seen) for i in obj]) 

 

return size 

 

 

def stripIfNotNone(s): 

"""Strip leading and trailing whitespace if the given object is not None. 

 

Parameters 

---------- 

s : `str`, optional 

Input string. 

 

Returns 

------- 

r : `str` or `None` 

A string with leading and trailing whitespace stripped if `s` is not 

`None`, or `None` if `s` is `None`. 

""" 

if s is not None: 

s = s.strip() 

return s 

 

 

class PrivateConstructorMeta(type): 

"""A metaclass that disables regular construction syntax. 

 

A class that uses PrivateConstructorMeta may have an ``__init__`` and/or 

``__new__`` method, but these can't be invoked by "calling" the class 

(that will always raise `TypeError`). Instead, such classes can be called 

by calling the metaclass-provided `_construct` class method with the same 

arguments. 

 

As is usual in Python, there are no actual prohibitions on what code can 

call `_construct`; the purpose of this metaclass is just to prevent 

instances from being created normally when that can't do what users would 

expect. 

 

..note:: 

 

Classes that inherit from PrivateConstructorMeta also inherit 

the hidden-constructor behavior. If you just want to disable 

construction of the base class, `abc.ABCMeta` may be a better 

option. 

 

Examples 

-------- 

Given this class definition:: 

class Hidden(metaclass=PrivateConstructorMeta): 

 

def __init__(self, a, b): 

self.a = a 

self.b = b 

 

This doesn't work: 

 

>>> instance = Hidden(a=1, b="two") 

TypeError: Hidden objects cannot be constructed directly. 

 

But this does: 

 

>>> instance = Hidden._construct(a=1, b="two") 

 

""" 

 

def __call__(cls, *args, **kwds): 

"""Disabled class construction interface; always raises `TypeError.` 

""" 

raise TypeError(f"{cls.__name__} objects cannot be constructed directly.") 

 

def _construct(cls, *args, **kwds): 

"""Private class construction interface. 

 

All arguments are forwarded to ``__init__`` and/or ``__new__`` 

in the usual way. 

""" 

return type.__call__(cls, *args, **kwds)