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tiktoken_wrapper.py
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tiktoken_wrapper.py
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import tiktoken
def num_tokens_from_messages(messages, model="gpt-3.5-turbo-0301"):
"""Returns the number of tokens used by a list of messages."""
try:
encoding = tiktoken.encoding_for_model(model)
except KeyError:
encoding = tiktoken.get_encoding("cl100k_base")
if model == "gpt-3.5-turbo-0301": # note: future models may deviate from this
num_tokens = 0
for message in messages:
num_tokens += 4 # every message follows <im_start>{role/name}\n{content}<im_end>\n
for key, value in message.items():
num_tokens += len(encoding.encode(value))
if key == "name": # if there's a name, the role is omitted
num_tokens += -1 # role is always required and always 1 token
num_tokens += 2 # every reply is primed with <im_start>assistant
return num_tokens
else:
raise NotImplementedError(f"num_tokens_from_messages() is not presently implemented for model {model}."
"See https://github.com/openai/openai-python/blob/main/chatml.md "
"for information on how messages are converted to tokens.")