"Instead of execution time, coding time is much more precious in such competitions"
Unfortunately, in such competitions you'll be competing against people who write C++ algos faster than normal people writing Python.
Unfortunately, in such competitions you'll be competing against people who write C++ algos faster than normal people writing Python.
That doesn't mean that there aren't also people who have done the same and still prefer python (or some other language) not for execution, but development speed (and bignum, larger standard library...)