A more

[Terry Reedy]

On 11/14/2019 10:24 AM, James Lu wrote:
> Where do I go to find a more complete specification for Python?

The Cpython code, the tests, and its actual behavior.

> I want to
> learn about common semi-internal language features used by popular
> libraries, because I am reimplementing Python.
> 
> The reference guide says:
> 
>> While I am trying to be as precise as possible, I chose to use English
>> rather than formal specifications for everything except syntax and lexical
>> analysis. This should make the document more understandable to the average
>> reader, but will leave room for ambiguities. *Consequently, if you were
>> coming from Mars and tried to re-implement Python from this document alone,
>> you might have to guess things and in fact you would probably end up
>> implementing quite a different language. *

I suspect that this is less true than when Guido wrote it.  There have 
been other implementations since, and the implementers have occasionally 
asked questions that resulted in the docs being clarified.

-- 
Terry Jan Reedy