import torch

!pip install torch

from transformers import AutoModelForCausalLM, AutoTokenizer

model = AutoModelForCausalLM.from_pretrained("gpt2")
tokenizer = AutoTokenizer.from_pretrained("gpt2")

inputs = tokenizer("Hugging Face is a startup based in New York City and Paris",
                   return_tensors="pt")

loss = model(input_ids=inputs["input_ids"],
             labels=inputs["input_ids"]).loss

loss = model(input_ids=inputs["input_ids"],
             labels=inputs["input_ids"]).loss
ppl = torch.exp(loss)

print(f"Perplexity: {ppl.item(): 2f}")