What's bad about Python?
Python is, on average, 35 times slower than equivalent C/C++ code, as much as 150 times slower for certain tasks on single-threaded problems. It get's worse with concurrency, where on threaded benchmarks running on quad-core machines, it can be as much as 450 times slower. The CPython implementation (the main canonical implementation of Python) has no thread-scalability except with asynchronous I/O, due to the global interpreter lock.
http://shootout.alioth.debian.org/u64q/which-programming-languages-are-fastest.php