Use dashes instead of underscores in filenames

Author: mlouhivu

numpy/input-output/solution/input-output.py

@@ -4,4 +4,4 @@
 filename = sys.argv[1]
 xy = np.loadtxt(filename)
 xy[:,1] += 2.5
-np.savetxt('new_' + filename, xy, fmt='%.6f', header='modified data')
+np.savetxt('new-' + filename, xy, fmt='%.6f', header='modified data')

numpy/input-output/solution/xy-coordinates.dat

@@ -0,0 +1 @@
+../xy-coordinates.dat