How to generate .engine?

I have Python code[use keras,yolov3]----GitHub - qqwweee/keras-yolo3: A Keras implementation of YOLOv3 (Tensorflow backend)
How to generate .engine?

You can convert keras → ONNX → TRT, please refer to below link for more details:

Importing ONNX in TRT:

You can also user trtexec command to generate TRT file:
https://github.com/NVIDIA/TensorRT/blob/master/samples/opensource/trtexec/README.md#example-4-running-an-onnx-model-with-full-dimensions-and-dynamic-shapes

You can also refer to below sample for Yolo to TRT conversion:

Thanks