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Of course it will catch as many error as possible, but when you compare python with C++ (or any compile vs runtime language), it's not accurate to say that all the errors you'll find will be somewhere undetected in a python program.
Just to bring one, there's many type in C++ that needed to be check where in python it doesn't matter at all. Like integer, in C++ the compiler need to check for int, long, unsigned, etc. In python, who cares? it's an integer. If you do some mixing in C++, the compiler will complain, but these errors are irrelevent in python. So as many errors in C++ are far less in python. (but I agree that some will not be check)
At the end it is a matter of design and the quality of code. Bad python code will end on error, bad c++ might throw a buffer overflow.
the first problem for portage that he said is :