When using edward, we always use from edward.models import Normal , but i didn't find the declaration of Normal in github
anybody who can tell me where is it
They are defined in edward/models/random_variables.py.
You import the Normal class like this:
from edward.models import Normal
This suggests looking in edward/models/__init__.py, which has this line:
from edward.models.random_variables import *
Looking in edward/models/random_variables.py we find this code:
from edward.models.random_variable import RandomVariable as _RandomVariable
from tensorflow.contrib import distributions as _distributions
# Automatically generate random variable classes from classes in
# tf.contrib.distributions.
_globals = globals()
for _name in sorted(dir(_distributions)):
_candidate = getattr(_distributions, _name)
if (_inspect.isclass(_candidate) and
_candidate != _distributions.Distribution and
issubclass(_candidate, _distributions.Distribution)):
# to use _candidate's docstring, must write a new __init__ method
def __init__(self, *args, **kwargs):
_RandomVariable.__init__(self, *args, **kwargs)
__init__.__doc__ = _candidate.__init__.__doc__
_params = {'__doc__': _candidate.__doc__,
'__init__': __init__}
_globals[_name] = type(_name, (_RandomVariable, _candidate), _params)
del _candidate
This goes through the tensorflow.contrib.distributions module looking for classes derived from tensorflow.contrib.distributions.Distribution (ignoring other attributes like e.g. the __file__ member of the module, or the base Distribution class itself). For each one, it does a bit of hacking (which only affects the generated documentation) then executes this key line:
_globals[_name] = type(_name, (_RandomVariable, _candidate), _params)
The type() built-in function creates a new type i.e. declares a new class. The second parameter is the list of base classes, which here is edward's RandomVariable class and the TensorFlow random variable class. Earlier it defined _globals to be globals(), which is a built-in function returning the dictionary of the module's variables. Therefore, in the case you're interested in, the line above is equivalent to the following:
from edward.models.random_variable import RandomVariable as EdRandVar
from tensorflow.contrib.distributions import Normal as TfNormal
Normal = type("Normal", (EdRandVar, TfNormal), {...})
Which in turn is equivalent to this (if you ignore the docstring stuff):
from edward.models.random_variable import RandomVariable as EdRandVar
from tensorflow.contrib.distributions import Normal as TfNormal
class Normal(EdRandVar, TfNormal):
pass