pprint.isreadable returns True for non-eval-able float and complex specials

Issue

isreadable is documented as returning True if the object's repr is readable by the interpreter — implying eval(pformat(obj)) == obj. For float and complex non-finite values, isreadable returns True, but the roundtrip fails — eval raises NameError since inf and nan aren't valid Python expressions.

Reproducer

import pprint

print(pprint.isreadable(float('inf')))        # True — but eval('inf') raises NameError
print(pprint.isreadable(float('nan')))        # True
print(pprint.isreadable(complex(float('inf'), 0)))  # True

CPython versions tested on:

CPython main branch

Operating systems tested on:

No response

Linked PRs

• gh-145116
• gh-145120

从 pprint.isreadable 开始，并运行针对非有限 float 和 complex 值的 reproducer。跟踪它们的表示是如何分类的，然后验证当求值该表示引发 NameError 时，isreadable 不再声称这些值是可读的；为这些情况添加或更新针对性测试。