**System Information**
CentOs, Intel graphics chip
**Blender Version**
Broken: 2.72b 9e963ae
**Short description of error**
If I try to print the result of a math node via python, I always getting 0.
**Exact steps for others to reproduce the error**
1. Create 2 value node with different values
2. Some math (e.g. subtract both values)
3.
```
>>> bpy.data.materials['Material'].node_tree.nodes['Math'].outputs['Value'].default_value
```
Result:
```
>>> 0.0
```