move data save to beginning to avoid confusion

I.py

@@ -18,7 +18,9 @@ else:
     for i in range(NUM_BANDS):
         band = RubberBand(N, a=1)
         lengths[i] = band.length/band.a
-
+    
+    np.save("data/lengths.npy", lengths)
+    
 # histogram
 bin_edges = np.arange(-N-1, N+1, 2)
 values, _ = np.histogram(lengths, bins=bin_edges)
@@ -63,6 +65,4 @@ plt.hlines(1, *xlim, color='r', linestyle='--')
 plt.xlim(xlim)
 plt.xlabel("$L/a$")
 plt.ylabel("$\hat{P}(L)/P(L)$")
-plt.show()
-
-np.save("data/lengths.npy", lengths)
+plt.show()