[pysdr]

Yep it's an alternative, for those getting started. My book doesn't actually involve using/creating a python library, so it's more of a tutorial type of thing. GNU Radio is great if you are doing a streaming-style RF app. It's also great if you want to share your app or individual blocks with others. It's not as good if your app is more packetized than streaming, or if you need GUI elements that don't come with GNU Radio. But if the only GUI you need is time/freq plots or waterfall/spectrograms, and various inputs, GNU Radio will save you a lot of time.