Why is this nested for loop faster in python? How can I make it faster in Matlab?

    ...code above...
J    = zeros(n_x,n_x,n_x); %Preallocation
ionf = zeros(n_x,n_x,n_x); %Preallocation
dens = zeros(n_x,n_x,n_x); %Preallocation
temp = zeros(n_x,n_x,n_x); %Preallocation
%loop
for i = 1:n_x
    for j = 1:n_x
        for k = 1:n_x
            data = strsplit(fgets(fin));
            J(i,j,k)    = single(str2double(data{1}));
            ionf(i,j,k) = single(str2double(data{2}));
            dens(i,j,k) = single(str2double(data{3}));
            temp(i,j,k) = single(str2double(data{4}));
        end
    end
end
...code below...

I translated some code from python to Matlab. Why is this nested for loop faster in python? How can I make it faster in Matlab? All variables are defined, I just need advice in the for loop speed. Thank you in advance

[Stephen23]

WHY: because they are different languages and work in different ways. It is slow because it uses a nested loops and slow conversions inside those loops (e.g. str2double).

FIX: Just replace the all of this code with textscan and it will be much faster.