Unless you are using CPython extensions, PyPy is usable as a drop-in replacement that's significantly faster in almost all cases. In order to notice any significant speed gain, the JIT needs a chance to "warm up" though, so on short running applications or on web applications for the first couple of requests PyPy can be slower than CPython.
Unless you are using CPython extensions, PyPy is usable as a drop-in replacement that's significantly faster in almost all cases. In order to notice any significant speed gain, the JIT needs a chance to "warm up" though, so on short running applications or on web applications for the first couple of requests PyPy can be slower than CPython.