Performance is a very broad term. It has many different meanings and in many cases it is defined incorrectly. You have probably heard statements similar to "Language X is faster than Python". However, that statement is inherently wrong. Python is neither fast nor slow; Python is a programming language and a language has no performance metrics whatsoever. If one were to say that the CPython interpreter is faster or slower than interpreter Y for language X, that would be possible. The performance characteristics of code can vary greatly between different interpreters. Just take a look at this small test:
# python3 -m timeit '"".join(str(i) for i in range(10000))' 100 loops, best of 3: 2.91 msec per loop # python2 -m timeit '"".join(str(i) for i in range(10000))' 100 loops, best of 3: 2.13 msec per loop # pypy -m timeit '"".join(str(i) for i in range(10000))' 1000 loops, best of 3: 677 usec per loop
Three different interpreters with all vastly different performance! All...