Python 2.7 convert 2d string array to float array - arrays

Question

I read the following string on a .txt file
{{1,2,3,0},{4,5,6,7},{8,-1,9,0}}
using lin = lin.strip() to remove '\n'
Then I replaced { and } to [ and ] using
lin = lin.replace ("{", "[")
lin = lin.replace ("}", "]")
My goal is to convert lin into a float 2d array. So I did
my_matrix = np.array(lin, dtype=float)
but i got an error message: "ValueError: could not convert string to float: [[1,2,3,0],[1,1,1,2],[0,-1,3,9]]"
Removing the dtype, i get an string array. I already tried to multiply lin by 1.0, make a copy of lin using .astype(float), but nothing seems to work.

Answer 1

I am using the JSON library to parse the contents of the file and then iterate through the arrays and converting each element into float. However an integer solution might already be enough for what you want. That one is much faster and shorter.
import json
fc = '{{1,2,3,0},{4,5,6,7},{8,-1,9,0}}'
a = json.loads(fc.replace('{','[').replace('}',']'))
print(a) # a is now array of integers. this might be enough
for linenumber, linecontent in enumerate(a):
for elementnumber, element in enumerate(linecontent):
a[linenumber][elementnumber] = float(element)
print(a) # a is now array of floats
Shorter solution
import json
fc = '{{1,2,3,0},{4,5,6,7},{8,-1,9,0}}'
a = json.loads(fc.replace('{','[').replace('}',']'))
print(a) # a is now array of integers. this might be enough
a = [[float(c) for c in b] for b in a]
print(a) # a is now array of floats
(works for both python 2 and 3)

Answer 2

import numpy as np
readStr = "{{1,2,3,0},{4,5,6,7},{8,-1,9,0}}"
readStr = readStr[2:-2]
# Originally read string is now -> "1,2,3,0},{4,5,6,7},{8,-1,9,0"
line = readStr.split("},{")
# line is now a list object -> ["1,2,3,0", "4,5,6,7", "8,-1,9,0"]
array = []
temp = []
# Now we iterate through 'line', convert each element into a list, and
# then append said list to 'array' on each iteration of 'line'
for string in line:
num_array = string.split(',')
for num in num_array:
temp.append(num)
array.append(temp)
temp = []
# Now with 'array' -> [[1,2,3,0], [4,5,6,7], [8,-1,9,0]]
my_matrix = np.array(array, dtype = float)
# my_matrix = [[1.0, 2.0, 3.0, 0.0]
# [4.0, 5.0, 6.0, 7.0]
# [8.0, -1.0, 9.0, 0.0]]
Although this may not be the most elegant solution, I think it is easy to follow and gives you exactly what you're looking for.