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Python | SymPy Permutation.descents() method
• Last Updated : 26 Aug, 2019

Permutation.descents() : descents() is a sympy Python library function that returns the position of descents in the permutation. Descents are the elements where a[i] > a[i+1]

Syntax : sympy.combinatorics.permutations.Permutation.descents()

Return : position of descents in the permutation

Code #1 : descents() Example

 `# Python code explaining``# SymPy.descents()`` ` `# importing SymPy libraries``from` `sympy.combinatorics.partitions ``import` `Partition``from` `sympy.combinatorics.permutations ``import` `Permutation`` ` `# Using from sympy.combinatorics.permutations.Permutation.descents() method `` ` `# creating Permutation``a ``=` `Permutation([[``2``, ``0``], [``3``, ``1``]])`` ` `b ``=` `Permutation([``1``, ``3``, ``5``, ``4``, ``2``, ``0``])`` ` ` ` `print` `(``"Permutation a - descents form : "``, a.descents())``print` `(``"Permutation b - descents form : "``, b.descents())`

Output :

Permutation a – descents form : 
Permutation b – descents form : [2, 3, 4]

Code #2 : descents() Example – 2D Permutation

 `# Python code explaining``# SymPy.descents()`` ` `# importing SymPy libraries``from` `sympy.combinatorics.partitions ``import` `Partition``from` `sympy.combinatorics.permutations ``import` `Permutation`` ` `# Using from sympy.combinatorics.permutations.Permutation.descents() method `` ` `# creating Permutation``a ``=` `Permutation([[``2``, ``4``, ``0``], ``                 ``[``3``, ``1``, ``2``],``                 ``[``1``, ``5``, ``6``]])`` ` ` ` `print` `(``"Permutation a - descents form : "``, a.descents())`

Output :

Permutation a – descents form : [0, 3, 5]

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