How to get a 2D numpy array contained in a string?

Question

I stored 2D numpy arrays into a pandas dataframe, which I stored into a csv file. While reading the csv file, I am struggling to get back my 2D numpy array as they are stored as type string... How could I get the numpy array that is inside the string?

For example I have '[1.34 5.43]' and I want to convert to [1.34 5.43]. Any way to convert numpy array interpreted as string into numpy array?

SOLUTION: This was the solution How to convert string representation of list to a list?

Does this answer your question? numpy reading a csv file to an numpy array — Mad Physicist
– Mad Physicist, Commented Jul 1, 2020 at 13:23
Does this answer your question? How do I read CSV data into a record array in NumPy? — wwii
– wwii, Commented Jul 1, 2020 at 13:25
How large were those arrays? It is awkward, though not impossiible to recover arrays that were saved a strings to a csv. It's better to use a different save method. — hpaulj
– hpaulj, Commented Jul 1, 2020 at 15:05

Ricky · Accepted Answer · 2020-07-01 13:33:40Z

0

You can use the genfromtxt function.

import numpy as np
#create the array 
arr=np.arange(20).reshape(4,5)
#save as a text file
np.savetxt("arr.csv", arr, delimiter=",")
from numpy import genfromtxt
#generate array from text file
my_data = genfromtxt('arr.csv', delimiter=',')
type(my_data)

Output

numpy.ndarray

edited Jul 1, 2020 at 13:33

answered Jul 1, 2020 at 13:26

Ricky

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5 Comments

user7924113 Over a year ago

That's not exactly what I want. The numpy arrays are stored as string in the csv file. When I load the csv file, I want that each cell to be interpreted as a numpy array and not as a string

Ricky Over a year ago

How does your csv file looks like ? Here the csv file is in string but genfromtxt converts into a numpy array type.

user7924113 Over a year ago

I don't want to store all the values as a numpy array. I want to load my values in a pandas dataframe with each value being a numpy array

Ricky Over a year ago

@user7924113 I think without any reproducible example of input and output it will be a bit hard to understand your problem

user7924113 Over a year ago

This was the solution stackoverflow.com/questions/1894269/…

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