Identify groups of continuous numbers in a list

Question

I\'d like to identify groups of continuous numbers in a list, so that:

myfunc([2, 3, 4, 5, 12, 13, 14, 15, 16, 17, 20])

Returns:

Answer 1

Using numpy + comprehension lists:
With numpy diff function, consequent input vector entries that their difference is not equal to one can be identified. The start and end of the input vector need to be considered.

import numpy as np
data = np.array([2, 3, 4, 5, 12, 13, 14, 15, 16, 17, 20])

d = [i for i, df in enumerate(np.diff(data)) if df!= 1] 
d = np.hstack([-1, d, len(data)-1])  # add first and last elements 
d = np.vstack([d[:-1]+1, d[1:]]).T

print(data[d])

Output:

 [[ 2  5]   
  [12 17]   
  [20 20]]

Note: The request that individual numbers should be treated differently, (returned as individual, not ranges) was omitted. This can be reached by further post-processing the results. Usually this will make things more complex without gaining any benefit.