tensorflow @tf.exports

tf.exports 的定義在 tensorflow.python.util.tf_export.py

主要是爲函數或者類增加新的__dict__

tf_export = functools.partial(api_export, api_name=TENSORFLOW_API_NAME)

api_export 是一個類，主要是將symbols 導入到Tesorflow API。
TENSORFLOW_API_NAME = “tensorflow”

類api_export 內部實現了一個__call__ 函數

def __call__(self, func):
    """Calls this decorator.
    Args:
      func: decorated symbol (function or class).
    Returns:
      The input function with _tf_api_names attribute set.
    Raises:
      SymbolAlreadyExposedError: Raised when a symbol already has API names
        and kwarg `allow_multiple_exports` not set.
    """
    api_names_attr = API_ATTRS[self._api_name].names
    api_names_attr_v1 = API_ATTRS_V1[self._api_name].names
    # Undecorate overridden names
    for f in self._overrides:
      _, undecorated_f = tf_decorator.unwrap(f)
      delattr(undecorated_f, api_names_attr)
      delattr(undecorated_f, api_names_attr_v1)

    _, undecorated_func = tf_decorator.unwrap(func)
    # set_attr 首先檢查api_names_attr是不是在undecorated_func的__dict__
    # 如果已經存在，會拋出SymbolAlreadyExposedError
    # 這裏的 api_names_attr 和 api_names_attr_v1
    '''
# Attribute values must be unique to each API.
API_ATTRS = {
    TENSORFLOW_API_NAME: _Attributes(
        '_tf_api_names',
        '_tf_api_constants'),
    ESTIMATOR_API_NAME: _Attributes(
        '_estimator_api_names',
        '_estimator_api_constants'),
    KERAS_API_NAME: _Attributes(
        '_keras_api_names',
        '_keras_api_constants')
}

API_ATTRS_V1 = {
    TENSORFLOW_API_NAME: _Attributes(
        '_tf_api_names_v1',
        '_tf_api_constants_v1'),
    ESTIMATOR_API_NAME: _Attributes(
        '_estimator_api_names_v1',
        '_estimator_api_constants_v1'),
    KERAS_API_NAME: _Attributes(
        '_keras_api_names_v1',
        '_keras_api_constants_v1')
}
對於TENSORFLOW_API_NAME ，則是 _tf_api_names 、 _tf_api_names_v1
    '''
    
    self.set_attr(undecorated_func, api_names_attr, self._names)
    self.set_attr(undecorated_func, api_names_attr_v1, self._names_v1)
    return func

例子：

class TestClassA(object):
    def __init__(self):
        self.a = 12
    
export_decorator_a = tf_export.tf_export('TestClassA', 'dadsa')
print("1:", TestClassA.__dict__)
a = export_decorator_a(TestClassA)
print("2:",TestClassA.__dict__)

# 被修飾後的類和原來的類是一致的
print(id(a))
print(id(TestClassA))

輸出：

1: {'__module__': '__main__', '__init__': <function TestClassA.__init__ at 0x7f5c40211f28>, '__dict__': <attribute '__dict__' of 'TestClassA' objects>, '__weakref__': <attribute '__weakref__' of 'TestClassA' objects>, '__doc__': None}
2: {'__module__': '__main__', '__init__': <function TestClassA.__init__ at 0x7f5c40211f28>, '__dict__': <attribute '__dict__' of 'TestClassA' objects>, '__weakref__': <attribute '__weakref__' of 'TestClassA' objects>, '__doc__': None, '_tf_api_names': ('TestClassA', 'dadsa'), '_tf_api_names_v1': ('TestClassA', 'dadsa')}
)
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