There's definitely some truth to this and I've seen it myself. Nonetheless, there is a point where these languages begin to have more similarities then differences. By the time I felt comfortable with C, Java, PHP and Ruby it only took me a couple of weeks to feel like I had a decent handle on Python.

That said, I'm sure there are a lot of Python specific techniques that still elude me and I continue to read through the source for libraries I'm using.