tf.lite.Interpreter

Interpreter interface for TensorFlow Lite Models.

tf.lite.Interpreter(
    model_path=None, model_content=None, experimental_delegates=None,
    num_threads=None
)

This makes the TensorFlow Lite interpreter accessible in Python. It is possible to use this interpreter in a multithreaded Python environment, but you must be sure to call functions of a particular instance from only one thread at a time. So if you want to have 4 threads running different inferences simultaneously, create an interpreter for each one as thread-local data. Similarly, if you are calling invoke() in one thread on a single interpreter but you want to use tensor() on another thread once it is done, you must use a synchronization primitive between the threads to ensure invoke has returned before calling tensor().

model_path Path to TF-Lite Flatbuffer file.
model_content Content of model.
experimental_delegates Experimental. Subject to change. List of TfLiteDelegate objects returned by lite.load_delegate().
num_threads Sets the number of threads used by the interpreter and available to CPU kernels. If not set, the interpreter will use an implementation-dependent default number of threads. Currently, only a subset of kernels, such as conv, support multi-threading.

ValueError If the interpreter was unable to create.

Methods

allocate_tensors

View source

allocate_tensors()

get_input_details

View source

get_input_details()

Gets model input details.

Returns
A list of input details.

get_output_details

View source

get_output_details()

Gets model output details.

Returns
A list of output details.

get_tensor

View source

get_tensor(
    tensor_index
)

Gets the value of the input tensor (get a copy).

If you wish to avoid the copy, use tensor(). This function cannot be used to read intermediate results.

Args
tensor_index Tensor index of tensor to get. This value can be gotten from the 'index' field in get_output_details.

Returns
a numpy array.

get_tensor_details

View source

get_tensor_details()

Gets tensor details for every tensor with valid tensor details.

Tensors where required information about the tensor is not found are not added to the list. This includes temporary tensors without a name.

Returns
A list of dictionaries containing tensor information.

invoke

View source

invoke()

Invoke the interpreter.

Be sure to set the input sizes, allocate tensors and fill values before calling this. Also, note that this function releases the GIL so heavy computation can be done in the background while the Python interpreter continues. No other function on this object should be called while the invoke() call has not finished.

Raises
ValueError When the underlying interpreter fails raise ValueError.

reset_all_variables

View source

reset_all_variables()

resize_tensor_input

View source

resize_tensor_input(
    input_index, tensor_size, strict=False
)

Resizes an input tensor.

interpreter = Interpreter(model_content=tflite_model)
interpreter.resize_tensor_input(0, [1, 224, 224, 3], strict=True)
interpreter.allocate_tensors()
interpreter.invoke()

Args
input_index Tensor index of input to set. This value can be gotten from the 'index' field in get_input_details.
tensor_size The tensor_shape to resize the input to.
strict Only unknown dimensions can be resized when strict is True. Unknown dimensions are indicated as -1 in the shape_signature attribute of a given tensor. (default False)

Raises
ValueError If the interpreter could not resize the input tensor.

set_tensor

View source

set_tensor(
    tensor_index, value
)

Sets the value of the input tensor.

Note this copies data in value.

If you want to avoid copying, you can use the tensor() function to get a numpy buffer pointing to the input buffer in the tflite interpreter.

Args
tensor_index Tensor index of tensor to set. This value can be gotten from the 'index' field in get_input_details.
value Value of tensor to set.

Raises
ValueError If the interpreter could not set the tensor.

tensor

View source

tensor(
    tensor_index
)

Returns function that gives a numpy view of the current tensor buffer.

This allows reading and writing to this tensors w/o copies. This more closely mirrors the C++ Interpreter class interface's tensor() member, hence the name. Be careful to not hold these output references through calls to allocate_tensors() and invoke(). This function cannot be used to read intermediate results.

Usage:

interpreter.allocate_tensors()
input = interpreter.tensor(interpreter.get_input_details()[0]["index"])
output = interpreter.tensor(interpreter.get_output_details()[0]["index"])
for i in range(10):
  input().fill(3.)
  interpreter.invoke()
  print("inference %s" % output())

Notice how this function avoids making a numpy array directly. This is because it is important to not hold actual numpy views to the data longer than necessary. If you do, then the interpreter can no longer be invoked, because it is possible the interpreter would resize and invalidate the referenced tensors. The NumPy API doesn't allow any mutability of the the underlying buffers.

WRONG:

input = interpreter.tensor(interpreter.get_input_details()[0]["index"])()
output = interpreter.tensor(interpreter.get_output_details()[0]["index"])()
interpreter.allocate_tensors()  # This will throw RuntimeError
for i in range(10):
  input.fill(3.)
  interpreter.invoke()  # this will throw RuntimeError since input,output

Args
tensor_index Tensor index of tensor to get. This value can be gotten from the 'index' field in get_output_details.

Returns
A function that can return a new numpy array pointing to the internal TFLite tensor state at any point. It is safe to hold the function forever, but it is not safe to hold the numpy array forever.