SymPy | Python中的 Prufer.prev()

Prufer.prev() ：prev()是一个 sympy Python库函数，它返回 Prufer 序列，它是当前序列之前的 delta。

Syntax :
sympy.combinatorics.Prufer.prufer.prev()

Return :
Prufer sequence that is delta before the current one

代码 #1：prev() 示例

# Python code explaining
# SymPy.Prufer.prev()
  
# importing SymPy libraries
from sympy.combinatorics import Permutation, Cycle
from sympy.combinatorics.prufer import Prufer
  
# Using from 
# sympy.combinatorics.prufer.Prufer.prev()
  
# Creating Prufer
a = Prufer([1, 2, 3], [2, 4, 5])
  
# prev value
print ("Prufer a prev : ", a.prev(1))

输出 ：

Prufer a prev : Prufer([1, 2, 4])

代码 #2：prev() 示例

# Python code explaining
# SymPy.Prufer.prev()
  
# importing SymPy libraries
from sympy.combinatorics import Permutation, Cycle
from sympy.combinatorics.prufer import Prufer
  
# Using from 
# sympy.combinatorics.prufer.Prufer.prev()
  
# Creating Prufer
b = Prufer([1, 2, 3, 2, 4, 5], [6, 7], [8])
  
# prev value
print ("Prufer b prev : ", b.prev(1))

输出 ：

Prufer b prev : Prufer([1, 2, 3, 2, 4, 4])