如何从给定文件中读取矩阵？

Question

我有一个文本文件，其中包含 N * M 维度的矩阵。

例如，input.txt 文件包含以下内容：

0,0,0,0,0,0,0,0,0,0
0,0,0,0,0,0,0,0,0,0
0,0,0,0,0,0,0,0,0,0
0,0,0,0,0,0,0,0,0,0
0,0,0,0,0,0,0,0,0,0
0,0,0,0,0,0,0,0,0,0
0,0,2,1,0,2,0,0,0,0
0,0,2,1,1,2,2,0,0,1
0,0,1,2,2,1,1,0,0,2
1,0,1,1,1,2,1,0,2,1

我需要编写 python 脚本，在其中可以导入矩阵。

我当前的 python 脚本是：

f = open ( 'input.txt' , 'r')
l = []
l = [ line.split() for line in f]
print l

输出列表是这样的

[['0,0,0,0,0,0,0,0,0,0'], ['0,0,0,0,0,0,0,0,0,0'], ['0,0,0,0,0,0,0,0,0,0'],
 ['0,0,0,0,0,0,0,0,0,0'], ['0,0,0,0,0,0,0,0,0,0'], ['0,0,0,0,0,0,0,0,0,0'],
 ['0,0,2,1,0,2,0,0,0,0'], ['0,0,2,1,1,2,2,0,0,1'], ['0,0,1,2,2,1,1,0,0,2'],
 ['1,0,1,1,1,2,1,0,2,1']]

我需要获取 int 形式的值。如果我尝试输入强制类型转换，它会抛出错误。

Answer 1

考虑

with open('input.txt', 'r') as f:
    l = [[int(num) for num in line.split(',')] for line in f]
print(l)

产生

[[0, 0, 0, 0, 0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0, 0, 0, 0, 0], [0, 0, 0, 0, 0, 0, 0, 0, 0, 0], [0, 0, 2, 1, 0, 2, 0, 0, 0, 0], [0, 0, 2, 1, 1, 2, 2, 0, 0, 1], [0, 0, 1, 2, 2, 1, 1, 0, 0, 2], [1, 0, 1, 1, 1, 2, 1, 0, 2, 1]]

注意，你必须用逗号分隔。

---

如果确实有空行，则更

l = [[int(num) for num in line.split(',')] for line in f ]

改为

l = [[int(num) for num in line.split(',')] for line in f if line.strip() != "" ]

Answer 2

您可以简单地使用numpy.loadtxt。
易于使用，您还可以指定分隔符、数据类型等。

具体来说，您需要做的就是：

import numpy as np
input = np.loadtxt("input.txt", dtype='i', delimiter=',')
print(input)

输出将是：

[[0 0 0 0 0 0 0 0 0 0]
 [0 0 0 0 0 0 0 0 0 0]
 [0 0 0 0 0 0 0 0 0 0]
 [0 0 0 0 0 0 0 0 0 0]
 [0 0 0 0 0 0 0 0 0 0]
 [0 0 0 0 0 0 0 0 0 0]
 [0 0 2 1 0 2 0 0 0 0]
 [0 0 2 1 1 2 2 0 0 1]
 [0 0 1 2 2 1 1 0 0 2]
 [1 0 1 1 1 2 1 0 2 1]]

Answer 3

你可以这样做：

fin = open('input.txt','r')
a=[]
for line in fin.readlines():
    a.append( [ int (x) for x in line.split(',') ] )

Answer 4

以下内容可以满足您的要求：

l = []
with open('input.txt', 'r') as f:
  for line in f:
    line = line.strip()
    if len(line) > 0:
      l.append(map(int, line.split(',')))
print l

Answer 5

您不应该编写 csv 解析器，在读取此类文件时考虑 csv 模块，并在读取后使用 with 语句关闭：

import csv

with open('input.txt') ad f:
    data = [map(int, row) for row in csv.reader(f)]

Answer 6

查看这个用于读取矩阵的一行小代码，

matrix = [[input() for x in range(3)] for y in range(3)]

该代码将读取 3*3 阶的矩阵。

Answer 7

import numpy as np
f = open ( 'input.txt' , 'r')
l = []
l = np.array([ line.split() for line in f])
print (l)
type(l)

输出：

<预><代码>[['0'] ['0'] ['0'] ['0,0,0,0,0,0,0,0,0,0,0']
['0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0']
['0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0']]

numpy.ndarray

Answer 8

以下代码将上述输入转换为矩阵形式：

f = open ('input.txt' , 'r')
l = []
l = [line.split() for line in f]
l=np.array(l)
l=l.astype(np.int)