使用python从文本文件导入矩阵

Question

I have two text files that have matrices written in them(not numpy matrices, so its a list of lists). These matrices are written in string format, so the text file looks like this : [[1,2,3],[3,4,5],[6,7,8]],[[3,3,3],[5,6,7],.....

I want to read this matrix back from the text file using python. I can't read using numpy as it gives ValueError: could not convert string to float

Is there anyway to do this? Would it be easier if I just wrote the matrix as a numpy matrix in the first place(I need to change code of a previous program for that, and was just wondering if there was a python way of loading matrices when it was stored as a string in a text file)?

Answer 1

You could make use of the ast module:

import ast

strArray =  "[[1,2,3],[3,4,5],[6,7,8]]"

# evaluates the array in string format and converts it to a python array object
array = ast.literal_eval(strArray)

note: For multiple nested arrays like you have, literal_eval will most likely convert the string into a tuple with nested arrays as elements. Just keep that in mind as you use this module.