Is there a way to know which codes on github are in python 3? So far, I haven't any mentionned.
Tks
Very simply:

Yes, you can find Python3 code.
No, you cannot do so effectively.

Code on GitHub is not identified by language and version -- obviously, since you would have found that in your investigations before coding.  Yes, you can generally determine the language of a code file, but only with detailed examination -- you would almost need to pass the file to a Python compiler and reject any with syntax errors.  This is not an effective process.
You can reduce the search somewhat by gleaning *.py files and then look for frequent, 3-specific features, such as all print commands using parentheses (coding style in Python 2, mandated in Python 3).  This merely reduces the problem; it does not give you a good request mechanism.
how can I find python 3 codes only on github?