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� Zdd� Zdd� Zdd� Zdd� Zdd� Zdd�dd�Z z ddl Z W n e y� Y n 0 e j ZZ dS )z.A Future class similar to the one in PEP 3148.)�Future� wrap_future�isfuture� N)� GenericAlias� )� base_futures)�events)�
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- Callbacks registered with add_done_callback() are always called
via the event loop's call_soon().
- This class is not compatible with the wait() and as_completed()
methods in the concurrent.futures package.
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zFuture.exceptionr< c C sB | j tkr | jj|| |d� n |du r.t�� }| j�||f� dS )z�Add a callback to be run when the future becomes done.
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zFuture.add_done_callbackc s< � fdd�| j D �}t| j �t|� }|r8|| j dd�< |S )z}Remove all instances of a callback from the "call when done" list.
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�zFuture.remove_done_callbackc C s8 | j tkr t�| j � d| ����|| _t| _ | �� dS )z�Mark the future done and set its result.
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