How I can transfer matrix in Python?

Question

#Example:
A = [[1,2,3,4],[4,3,2,1],[3,2,1,4],[2,1,4,3]]
#How I can transform matrix A become matrix B 
#with matrix B I want to become...
B = [[1],
     [2],
     [3],
     [4],
     [4],
     [3],
     [2],
     [1],
     [3],
     [2],
     [1],
     [4],
     [2],
     [1],
     [4],
     [3]]

And when I save .txt or .csv how I can transfer data without [] in all of the data?

Answer 1

Write full

A = [[1,2,3,4],[4,3,2,1],[3,2,1,4],[2,1,4,3]]
B = []

for Am in A:
  for x in Am:
    B.append([x])

print (B)

Write short

A = [[1,2,3,4],[4,3,2,1],[3,2,1,4],[2,1,4,3]]
B = [[x] for Am in A for x in Am]
print (B)

Link Example