Beat Detection (audio)

[erROAR]

Hey, this is my first post in the forums, and I'm fairly new to Python, so bear with me...

I'm looking at ways to detect the beat in an audio file.

I know that the general idea is to run a loop like so:

while song is still playing:
   if low frequency is above a certain amplitude:
      call function dosomething

I'm pretty sure there is no built-in library that includes amplitude detection.
What would you pros recommend I use/do?

Thanks for the help in advance