从文件中读取二维数组

Question

Im working on a simulation project in Python and encountered a problem. I need to save a 2D array to a file, so I can use data from it later. The initial list looks like this:

int_array3 = [[14,5], [9,3], [25,5]]
#writing to file:
with open('data.txt', 'w') as f:
for num in int_array3:
    f.write("%s\n" % num)

The data in file looks like this:

[14  5]
[9 3]
[25  6]

I have tired this piece of code to read it, but it is not an integer list.

with open('data.txt', 'r') as f:
result = f.readlines()
result = [x.strip() for x in result]

The result list looks like this:

['[14  5]', '[9 3]', '[25  6]']

Can someone recommend me how to make it work? I want the result list to be shaped the same way my initial list was. I am using numpy.

Answer 1

How about writing only numbers without [] to file? You can achieve that with nested for loop during writing to file. Just remember to separate numbers (with space for example). Then, you could read your file line by line, use split() , and then you'll have an array of numbers, but for now it's an array of strings. To make numbers out of it, you'd need to cast string numbers to int. I think the easiest way would be using list comprehension to build new list of numbers.

To illustrate the above, your writing code would be like this:

int_array3 = [[14,5], [9,3], [25,5]]
#writing to file:
with open('data.txt', 'w') as f:
for vec in int_array3:
    for number in vec:
        f.write("%d " % number)
    f.write("\n")

And you could read your wile with:

with open('data.txt', 'r') as f:
for line in f:
    vector = [int(x) for x in line.split()]
    #Do something with vector variable

Answer 2

You can try using eval() to convert the string to an array like so:

A = ['[14  5]', '[9 3]', '[25  6]']
arr = []

for i in range(len(A)):
    l = eval(A[i].split()[0] + ',' + A[i].split()[1])
    arr.append(l)

print(A)
# [[14, 5], [9, 3], [25, 6]]

Feel free to ask for clarifications