While there isn't anything intrinsically wrong with using index(), the premise of this issue is essentially a claim that most Python code that uses int() is wrong.  That seems rather bold and flies in the face of common practices.  I don't really like the trend of constantly rearranging code in awkward ways to solve problems that no one actually has.

Also, I disagree with the notion that the downstream functions in the random module should be written in C.  That makes them more bug prone and opaque (like when Victor broken seeding for 3.6.0).  The trend for rewriting in C should be restricted to core building blocks like the underlying Mersenne Twister.  Otherwise, we have to do dual maintenance for years and essentially advertise to people that we don't think our own language is good enough to use.  Over time, I am less and less able to show people standard library code as it has become complexified with coding strategies well beyond the norms of day to day Python programmers.  ISTM that most proposals to rewrite something in C come from folks who like rewriting things in C rather than from users or from people who do long term maintenance of the modules.  Sidenote: we're now getting new core devs who don't read or write C, so each transformation like them excludes their ability to participate).