Python用于追赶法解方程组

 A=[]            #定义一个列表存储系数矩阵

    
 L=[]
    
 U=[]
    
 Y=[]
    
 a=-1
    
 b=4
    
 c=-1
    
 S = a           #   S----γ
    
 T=[]            #   T----β
    
 R=[]            #   R----α
    
 Answer_X=[]
    
 N=5
    
 X=['x1','x2','x3','x4','x5']
    
 f=[100,200,200,200,100]
    
 def agmA():
    
     for i in range(N):
    
     A.append([])
    
     for j in range(N):
    
         if i==j:
    
             A[i].append(b)
    
         elif i+1==j:
    
             A[i].append(c)
    
         elif i==j+1:
    
             A[i].append(a)
    
         else: