python代码末尾的“ None”打印

Question

I'm trying to get a python program to take a .dat file and read it into a matrix. I've it working for the most part, however "None" keeps printing at the end of the statement.

import sys

def main():

  matrix = generateMatrixFromFile(sys.argv[1])

  print(printMatrix(matrix))

def generateMatrixFromFile(fname):
  fp = open(fname, "r")
  row = fp.readlines()
  matrix = []
  for i in range(0, len(row), 1):
    token = row[i].split(" ")
    token[-1] = token[-1].replace('\n', '')
    matrix.append(token)
  fp.close()
  return matrix

def printMatrix(matrix):
  for i in range(0, len(matrix), 1):
    for j in range(0, len(matrix[i]), 1):
      print(matrix[i][j], sep=" ", end=" ")
    print()

main()

Answer 1

This line:

print(printMatrix(matrix)) 

is printing the return value of your function, which is None .

Just calling printMatrix(matrix) should make the result as you expected.

Answer 2

Remove the print on this line:

print(printMatrix(matrix))

Having it makes Python print the return value of printMatrix , which is None .

Answer 3

您的方法printMatrix(matrix)返回任何内容（ None ），并在其上调用打印（ print(printMatrix(matrix)) ）