extracting rows with specific values form a nested numpy array

Question

I have a numpy array as follow:

array([[0.603893  , 0.39610702],
   [0.6546377 , 0.34536234],
   [0.6454333 , 0.3545667 ],
   ...,
   [0.5815867 , 0.4184133 ],
   [0.52462864, 0.4753714 ],
   [0.4026965 , 0.5973035 ]], dtype=float32)

I want to extract the rows that the value of the first item is between say 0.2 to 0.5, How can I do this?

Where is the best place that I read about these type of tricks?

Answer 1

You can do that easily with: a[(a[:, 0] >= 0.2) & (a[:, 0] < 0.5)].

As for the information, the Numpy website is a good start... It contains tutorials and the documentation (with useful examples). Past StackOverflow answers also help to solve many Numpy-related problems (the ones with the highest votes can be useful to learn interesting tricks that can be often applied).