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pythonrangeconcatenation

Combining a list of ranges in python

What is the easiest way to construct a list of consecutive integers in given ranges, like this?

[1,2,3,4,5,6,7,  15,16,17,18,19,  56,57,58,59]

I know the start and end values of each group. I tried this:

ranges = (  range(1,8),
            range(15,20),
            range(56,60)  )
Y = sum( [ list(x) for x in  ranges ] )

which works, but seems like a mouthful. And in terms of code legibility, the sum() is just confusing. In MATLAB it's just

Y = [ 1:7, 15:19, 56:59 ]

Is there an better way? Can use numpy if easier.

Bonus question

Can anybody explain why it doesn't work if I use a generator for the sum?

Y = sum( (list(x) for x in ranges) )

TypeError: unsupported operand types for +: 'int' and 'list'

Seems like it doesn't know the starting value should be [] rather than 0!

Solution

  • The matlab syntax has it's equivalent in with numpy.r_:

    import numpy as np

np.r_[1:7, 15:19, 56:59]

    output: array([ 1, 2, 3, 4, 5, 6, 15, 16, 17, 18, 56, 57, 58])

    For a list:

    np.r_[1:7, 15:19, 56:59].tolist()

    output: [1, 2, 3, 4, 5, 6, 15, 16, 17, 18, 56, 57, 58]