inspect.signature() builds a Signature whose every Parameter goes through the public Parameter constructor, which validates the name and the kind on each call. When the parameters come from a function's own code object, the names are already valid identifiers and the kinds are already the canonical constants, so that validation re-checks facts that are guaranteed to hold. Signature introspection runs constantly across the ecosystem — web frameworks resolving view and dependency arguments, click building commands, pytest wiring fixtures, serialization and validation layers — usually once per function and often at import time while an application is assembled.

This adds an internal Parameter._create() used only by _signature_from_function, the trusted caller that reads parameters from a code object. It populates the instance directly and skips the redundant checks. The one case that still needs the constructor's handling, a comprehension's implicit .0 argument, is detected and deferred to it. The public Parameter() constructor and all of its validation are untouched, so every other caller behaves exactly as before.

Taking the signature of 400 real callables collected from popular packages (requests, click, jinja2, sqlalchemy, werkzeug, flask and others) improves from 1.46 ms to 1.16 ms, 26% faster.

import inspect, importlib, pyperf

names = ["requests", "click", "jinja2", "sqlalchemy", "werkzeug", "flask",
         "urllib3", "rich.console", "json", "argparse", "logging", "http.client",
         "email.message", "configparser", "xml.etree.ElementTree", "subprocess"]
funcs = []
for name in names:
    try:
        mod = importlib.import_module(name)
    except ImportError:
        continue
    for attr in dir(mod):
        obj = getattr(mod, attr, None)
        if inspect.isfunction(obj):
            funcs.append(obj)
        elif inspect.isclass(obj):
            funcs.extend(m for m in vars(obj).values() if inspect.isfunction(m))
good = []
for f in funcs:
    try:
        inspect.signature(f); good.append(f)
    except (ValueError, TypeError):
        pass
good = good[:400]

runner = pyperf.Runner()
runner.metadata["n_callables"] = len(good)
runner.bench_func("inspect.signature over %d callables" % len(good),
                  lambda: [inspect.signature(f) for f in good])

Resolves #150816.