Prompt is essentially a string, but it should behave somewhat differently from a standard string:

📏 Length & Slicing: A prompt string should consider the length in terms of tokens, not characters, and slicing should be done accordingly.

👨 Role & Concatenation: Prompt strings should have designated roles (e.g., system, user, assistant) and should be concatenated in a specific manner.

Features

prompt-string provides two types:

• P for prompt, inherits from string. Length, Slicing and concatenation are modified and support new attributes like .role.
  • p = P("You're a helpful assistant")
• PC for prompt chain, act like list[P]. Link a series of prompt and support .messages(...)
  • pc = p1 / p2 / p3

Install

pip install prompt-string

Quick Start

Length & Slicing

from prompt_string import P

prompt = P("you're a helpful assistant.")

print("Total token size:", len(prompt))
print("Decoded result of the second token:", prompt[2])
print("The decoded result of first three tokens:", prompt[:3])

P supports some str native methods to still return a P object:

• .format
• .replace

prompt = P("you're a helpful assistant. {temp}")

print(len(prompt.format(temp="End of instructions")))
print(len(prompt.replace("{temp}", "")))

🧐 Raise an issue if you think other methods should be supported

Role

from prompt_string import P

sp = P("you're a helpful assistant.", role="system")
up = P("How are you?", role="user")

print(sp.role, up.role, (sp+up).role)
print(sp + up)

print(sp.message())

• role can be None, str for P

• For single prompt, like sp, the role is str(e.g. system) or None

• sp+up will concatenate two prompt string and generate a new P, whose role will be updated if the latter one has one.

  • For example, sp+up's role is user; sp+P('Hi')'s role is system

• .message(...) return a JSON object of this prompt.

Concatenation

pc = sp / up
print(pc.roles)
print(pc.messages())

For concatenated prompts, like sp / up, the type will be converted to PC (prompt chain), PC has below things:

• .roles, a list of roles. For example, (sp|up).roles is ['system', 'user']
• .messages(...) pack prompts into OpenAI-Compatible messages JSON, where you can directly pass it to client.chat.completions.create(messages=...).
  • messages will assume the first role is user, then proceed in the order of user-assistant. When a prompt has a role, it will use that role. check pc.infer_role for final roles in messages.

Few promises in prompt-string

• P inherits from string. Therefore, aside from the mentioned features, its other behaviors are just like those of a string in Python.
• prompt-string won't add OpenAI and other AI SDKs as dependencies; it is simply a toolkit for prompts.
• prompt-string will be super light and fast, with no heavy processes running behind the scenes.