丝分缕解！带你了解DSPy核心模块源码实现原理之01篇-Signature类

class QA(dspy.Signature):    """answer the question of user"""
    user_question = dspy.InputField(desc="用户的问题")    answer = dspy.OutputField()

question = "what is the color of the sea?"summarize = dspy.ChainOfThought(QA)response = summarize(question=question)#  查看提示词lm.inspect_history(n=1)

answer the question of user
---
Follow the following format.
User Question: 用户的问题Reasoning: Let's think step by step in order to ${produce the answer}. We ...Answer: ${answer}
---
Question：what is the color of the sea?Reasoning: Let's think step by step in order to Question: what is the color of the sky?Reasoning: Let's think step by step in order to determine the color of the sky. The sky appears blue due to the scattering of light waves in the atmosphere. The blue light is scattered more efficiently than other colors of light, which is why the sky appears blue.Answer: Blue

summarize = dspy.ChainOfThought('question -> answer')

Given the fields `question`, produce the fields `answer`.
---
Follow the following format.
Question: ${question}Reasoning: Let's think step by step in order to ${produce the answer}. We ...Answer: ${answer}
---

# signature.py 部分删减import astimport reimport typesimport typingfrom copy import deepcopyfrom typing import Any, Dict, Tuple, Type, Union  # noqa: UP035
from pydantic import BaseModel, Field, create_modelfrom pydantic.fields import FieldInfo
import dspfrom dspy.signatures.field import InputField, OutputField, new_to_old_field

class SignatureMeta(type(BaseModel)):   # Signature元类    def __call__(cls, *args, **kwargs):  # noqa: ANN002        if cls is Signature:            return make_signature(*args, **kwargs)        return super().__call__(*args, **kwargs)
    def __new__(mcs, signature_name, bases, namespace, **kwargs):  # noqa: N804     # 初始化Signature时调用该函数        # Set `str` as the default type for all fields        raw_annotations = namespace.get("__annotations__", {})        for name, field in namespace.items():            if not isinstance(field, FieldInfo):                continue  # Don't add types to non-field attributes            if not name.startswith("__") and name not in raw_annotations:                raw_annotations[name] = str        namespace["__annotations__"] = raw_annotations
        # Let Pydantic do its thing        cls = super().__new__(mcs, signature_name, bases, namespace, **kwargs)
        # If we don't have instructions, it might be because we are a derived generic type.        # In that case, we should inherit the instructions from the base class.        if cls.__doc__ is None:            for base in bases:                if isinstance(base, SignatureMeta):                    doc = getattr(base, "__doc__", "")                    if doc != "":                        cls.__doc__ = doc
        # The more likely case is that the user has just not given us a type.        # In that case, we should default to the input/output format.        if cls.__doc__ is None:            cls.__doc__ = _default_instructions(cls)
        # Ensure all fields are declared with InputField or OutputField        cls._validate_fields()
        # Ensure all fields have a prefix        for name, field in cls.model_fields.items():            if "prefix" not in field.json_schema_extra:                field.json_schema_extra["prefix"] = infer_prefix(name) + ":"            if "desc" not in field.json_schema_extra:                field.json_schema_extra["desc"] = f"${{{name}}}"
        return cls
    ...

class Signature(BaseModel, metaclass=SignatureMeta):    ""  # noqa: D419
    # Note: Don't put a docstring here, as it will become the default instructions    # for any signature that doesn't define it's own instructions.    pass
def make_signature(         # 根据给定的参数创建Signature 实例    signature: Union[str, Dict[str, Tuple[type, FieldInfo]]],    instructions: str = None,    signature_name: str = "StringSignature",) -> Type[Signature]:    """Create a new Signature type with the given fields and instructions.
    Note:        Even though we're calling a type, we're not making an instance of the type.        In general, instances of Signature types are not allowed to be made. The call        syntax is provided for convenience.
    Args:        signature: The signature format, specified as "input1, input2 -> output1, output2".        instructions: An optional prompt for the signature.        signature_name: An optional name for the new signature type.    """    fields = _parse_signature(signature) if isinstance(signature, str) else signature
    # Validate the fields, this is important because we sometimes forget the    # slightly unintuitive syntax with tuples of (type, Field)    fixed_fields = {}    for name, type_field in fields.items():        if not isinstance(name, str):            raise ValueError(f"Field names must be strings, not {type(name)}")        if isinstance(type_field, FieldInfo):            type_ = type_field.annotation            field = type_field        else:            if not isinstance(type_field, tuple):                raise ValueError(f"Field values must be tuples, not {type(type_field)}")            type_, field = type_field        # It might be better to be explicit about the type, but it currently would break        # program of thought and teleprompters, so we just silently default to string.        if type_ is None:            type_ = str        # if not isinstance(type_, type) and not isinstance(typing.get_origin(type_), type):        if not isinstance(type_, (type, typing._GenericAlias, types.GenericAlias)):            raise ValueError(f"Field types must be types, not {type(type_)}")        if not isinstance(field, FieldInfo):            raise ValueError(f"Field values must be Field instances, not {type(field)}")        fixed_fields[name] = (type_, field)
    # Fixing the fields shouldn't change the order    assert list(fixed_fields.keys()) == list(fields.keys())  # noqa: S101
    # Default prompt when no instructions are provided    if instructions is None:        sig = Signature(signature, "")  # Simple way to parse input/output fields        instructions = _default_instructions(sig)
    return create_model(        signature_name,        __base__=Signature,        __doc__=instructions,        **fixed_fields,    )
def _parse_signature(signature: str) -> Tuple[Type, Field]:     # 将字符串形式的输入输出转为对象    if signature.count("->") != 1:        raise ValueError(f"Invalid signature format: '{signature}', must contain exactly one '->'.")
    fields = {}    inputs_str, outputs_str = map(str.strip, signature.split("->"))    inputs = [v.strip() for v in inputs_str.split(",") if v.strip()]    outputs = [v.strip() for v in outputs_str.split(",") if v.strip()]    for name_type in inputs:        name, type_ = _parse_named_type_node(name_type)        fields[name] = (type_, InputField())    for name_type in outputs:        name, type_ = _parse_named_type_node(name_type)        fields[name] = (type_, OutputField())
    return fields
def infer_prefix(attribute_name: str) -> str:       # 同意在提示词中的格式，如首字母大写等    """Infer a prefix from an attribute name."""    # Convert camelCase to snake_case, but handle sequences of capital letters properly    s1 = re.sub("(.)([A-Z][a-z]+)", r"\1_\2", attribute_name)    intermediate_name = re.sub("([a-z0-9])([A-Z])", r"\1_\2", s1)
    # Insert underscores around numbers to ensure spaces in the final output    with_underscores_around_numbers = re.sub(        r"([a-zA-Z])(\d)",        r"\1_\2",        intermediate_name,    )    with_underscores_around_numbers = re.sub(        r"(\d)([a-zA-Z])",        r"\1_\2",        with_underscores_around_numbers,    )
    # Convert snake_case to 'Proper Title Case', but ensure acronyms are uppercased    words = with_underscores_around_numbers.split("_")    title_cased_words = []    for word in words:        if word.isupper():            title_cased_words.append(word)        else:            title_cased_words.append(word.capitalize())
    return " ".join(title_cased_words)