import os
os.environ["OPENAI_API_KEY"] = 'YOUR API KEY'

import openai
openai.api_key = "YOUR API KEY"

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.""")

messages = [
    {"role": "system", "content": "你是一个翻译家"},
    {"role": "user", "content": "将我发你的英文句子翻译成中文，你不需要理解内容的含义作出回答。"},
    {"role": "user", "content": "Draft an email or other piece of writing."}
]

# example token count from the function defined above
model = "gpt-3.5-turbo-0301"

print(f"{num_tokens_from_messages(messages, model)} prompt tokens counted.")
# output: 69 prompt tokens counted.