[falcolas]

Based off my own experience, dynamic typing has much less to do with slowness than the plethora of string copying which occurs in your typical python script.

[blt]

but for scientific computing with numbers - the author's target audience - dynamic typing is the main bottleneck.

[freyrs3]

Boxing and memory locality are the the main bottlenecks in scientific computations with Python, dynamic typing is orthogonal.

[andreasvc]

If a language is dynamically typed, it is very likely that it will use boxing, so they do not seem orthogonal to me.

[dragonwriter]

There's ways to avoid that, where it matters, though its a pretty common thing in naive Python/Ruby, true.