# Results

After an analysis you read results through `stage.output`. A stage in this context is a so-called calculation stage, which can be both a stage and a model without stages. As long as it it calculated and carries results it considered a calculation stage. Results follow a fixed hierarchy: from the stage down to a single value on one element.

```text
Calculation stage
  └── output                                  StageOutput
        ├── global_results                    Result
        ├── critical_results                  CriticalResults
        ├── solid, plate, ..., line_reaction  ResultIndexer
        │     └── [i]                         ElementIndexer
        │           ├── general               GeneralProperties
        │           ├── topology              Topology
        │           ├── material              PropertyContainer
        │           └── results               PropertyContainer
        │                 └── ... .<field>    ElementResult (unit, value)
        └── step[i]                           StepOutput
              ├── critical_results            CriticalResults
              └── solid, plate, ...           ResultIndexer
```
All these object are further described on their own page in this section.
Each level is reached with an attribute or an index, so a single value is one expression:

```python
project = gx.get_current_project()
project.run_analysis()
stage = project.get_models_and_stages()[0]
out = stage.output

out.global_results.factor_of_safety                 # stage Factor of Safety
out.critical_results.u_norm_max                     # maximum normalized displacement
out.plate[2].results.final_forces.M_y.value         # values on plate element 2
out.plate[2].topology.X                             # node X coordinates
[s.critical_results.u_norm_max for s in out.step]   # per-step max normalized displacement
```

## Levels

| Object | Reached by | Holds |
| --- | --- | --- |
| [StageOutput](/python/functions/objects/results/StageOutput) | `stage.output` | Everything below; the final step's results |
| [Result](/python/functions/objects/results/Result) | `.global_results` | Factor of safety, load multiplier, max displacement |
| [CriticalResults](/python/functions/objects/results/CriticalResults) | `.critical_results` | Min/max displacements, stresses and forces of a step |
| [StageResults](/python/functions/objects/results/StageResults) | *(base class)* | The result groups `solid`, `plate`, `point_reaction`, ... |
| [ResultIndexer](/python/functions/objects/results/ResultIndexer) | `.plate`, `.solid`, ... | All elements of one group; supports `len()`, `[i]` and iteration |
| [ElementIndexer](/python/functions/objects/results/ElementIndexer) | `.plate[i]` | One element: `general`, `topology`, `material`, `results` |
| [GeneralProperties](/python/functions/objects/results/GeneralProperties) | `.general` | Material name, material model and shape ID |
| [Topology](/python/functions/objects/results/Topology) | `.topology` | Node indices and X, Y, Z coordinates |
| [PropertyContainer](/python/functions/objects/results/PropertyContainer) | `.results`, `.material` | Nested result fields or material parameters |
| [ElementResult](/python/functions/objects/results/ElementResult) | `.results. ... .<field>` | `unit` and `value` (one entry per element point) |
| [StepOutput](/python/functions/objects/results/StepOutput) | `.step[i]` | The same groups and critical results for one step |
| [MaterialPointOutput](/python/functions/objects/results/MaterialPointOutput) | `test.output` | Material point test output; same structure, no `global_results` |

## Good to know
- **Repeated extraction of results from GX** is cumbersome for the program and will slow down scripts. It is preferable to extract the output to Python once and only interacting with the object from there. An example of this follows.
```python
#Bad practice
[stage.output.critical_results.u_norm_max for s in out.step] #Interacts with GX API at every step
#Preferable
out = stage.output #Results are extracted once
[s.critical_results.u_norm_max for s in out.step] #Only interacts with the Python object
```
- **Explore with `repr()`.** The fields in `CriticalResults` and `PropertyContainer` depend on the analysis type and element type. Print the object to list what is available at that level.
- **Steps.** `step` exists only when the analysis has more than one step. The top-level results of `stage.output` are the results of the last step.