I have a file.cc that contains an array of doubles values, as seen here:
double values[][4] = {
{ 0.1234, +0.5678, 0.1222, 0.9683 },
{ 0.1631, +0.4678, 0.2122, 0.6643 },
{ 0.1332, +0.5678, 0.1322, 0.1683 },
{ 0.1636, +0.7678, 0.7122, 0.6283 }
... continue
}
How can I export these values to a Python list?
I cannot touch these files because they belong to an external library, subject to modification. Exactly, I want to be able to update the library without affecting my code.
This is pretty much answered in this other SO post.
But I will add a bit here. You need to define a type then use the in_dll method.
From your example I made a so with those values in values. I hope you have an idea how big it is or can find out from other vars in the library, otherwise this is a seg fault waiting to happen.
import ctypes
lib = ctypes.CDLL('so.so')
da = ctypes.c_double*4*4
da.in_dll(lib, "values")[0][0]
# 0.1234
da.in_dll(lib, "values")[0][1]
# 0.5678
da.in_dll(lib, "values")[0][2]
# 0.1222
From here I would just loop over them reading into a list.
How about using a temporary file? Put the matrix in it by C and read them by python.
In file.cc, write a function to save the matrix to a file.
int save_to_file(double matrix[][4],int row) {
int i,j;
FILE *fp;
fp=fopen("tmp","w");
for(i=0;i<row;i++)
for(j=0;j<4;j++) {
fprintf(fp,"%f",matrix[i][j]);
if(j==3)
fprintf(fp,"\n",matrix[i][j]);
else
fprintf(fp," ",matrix[i][j]);
}
fclose(fp);
return 0;
}
and read them by a Python script like this:
tmp=open('tmp')
L = []
for line in tmp:
newline = []
t = line.split(' ')
for string in t:
newline.append(float(string))
L.append(newline)
tmp.close()
for row in L:
for number in row:
print "%.4f" %number
print " "
file.ccshould be some kind of C library to be used by a python program or an independent program? In case A you could check forctypes,cythonor write a small python C extension; in the second case you simply have to use some kind of IPC(exactly as if the python program was a different C program).