Flatten nested lists

sage.misc.flatten.flatten(in_list, ltypes=(<class 'list'>, <class 'tuple'>), max_level=9223372036854775807)

Flatten a nested list.

INPUT:

  • in_list – a list or tuple
  • ltypes – optional list of particular types to flatten
  • max_level – the maximum level to flatten

OUTPUT:

a flat list of the entries of in_list

EXAMPLES:

sage: flatten([[1,1],[1],2])
[1, 1, 1, 2]
sage: flatten([[1,2,3], (4,5), [[[1],[2]]]])
[1, 2, 3, 4, 5, 1, 2]
sage: flatten([[1,2,3], (4,5), [[[1],[2]]]],max_level=1)
[1, 2, 3, 4, 5, [[1], [2]]]
sage: flatten([[[3],[]]],max_level=0)
[[[3], []]]
sage: flatten([[[3],[]]],max_level=1)
[[3], []]
sage: flatten([[[3],[]]],max_level=2)
[3]

In the following example, the vector is not flattened because it is not given in the ltypes input.

sage: flatten((['Hi',2,vector(QQ,[1,2,3])],(4,5,6)))
['Hi', 2, (1, 2, 3), 4, 5, 6]

We give the vector type and then even the vector gets flattened:

sage: tV = sage.modules.vector_rational_dense.Vector_rational_dense
sage: flatten((['Hi',2,vector(QQ,[1,2,3])], (4,5,6)),
....:         ltypes=(list, tuple, tV))
['Hi', 2, 1, 2, 3, 4, 5, 6]

We flatten a finite field.

sage: flatten(GF(5))
[0, 1, 2, 3, 4]
sage: flatten([GF(5)])
[Finite Field of size 5]
sage: tGF = type(GF(5))
sage: flatten([GF(5)], ltypes = (list, tuple, tGF))
[0, 1, 2, 3, 4]

Degenerate cases:

sage: flatten([[],[]])
[]
sage: flatten([[[]]])
[]