Retrieving results

In this section, we describe how to get the results of a calculation after it has been parsed by AiiDA, or the input and output of a generic Node. When a calculation is done on the remote computer, AiiDA will retrieve the results and try to parse the results with the default parser, if one is available for the given calculation. These results are stored in new nodes, and connected as output of the calculation. Of course, it is possible to directly check the output nodes for a given calculation and get their content. However, AiiDA provides a way to directly access the results, using the CalculationResultManager class, described in the next section.

The CalculationResultManager


Before getting the calculation results, we need a correctly finished and parsed JobCalculation. For example this can be a Quantum ESPRESSO pw.x calculation. You can load such a calculation – we’ll call it calc – with the command

from aiida.orm import load_node
calc = load_node(YOURPK)

either in verdi shell, or in a python script (as described here). YOURPK should be substituted by a valid calculation PK in your database.

Using the CalculationResultManager instance

Each JobCalculation has a res attribute that is a CalculationResultManager instance and gives direct access to parsed data. You can access it as


To get all the possible keys that were parsed, you can convert the instance into a list. For instance, if you type

print list(calc.res)

you will get something like this:

[u'rho_cutoff', u'energy', u'energy_units', ...]

(the list of keys has been cut for clarity: you will get many more keys).

Once you know which keys have been parsed, you can access the parsed value simply as an attribute of the res CalculationResultManager. For instance, to get the final total energy, you can use


that will print the total energy in units of eV, as also stated in the energy_units key

print calc.res.energy_units

Similarly, you can get any other parsed value, for any code that provides a parser.


The CalculationResultManager is also integrated with the iPython/verdi shell completion mechanism: if calc is a valid JobCalculation, you can type


and then press the TAB key of the keyboard to get/complete the list of valid parsed properties for the calculation calc.

Node input and output

In the following, we will show the methods to access the input and output nodes of a given node.

Again, we start by loading a node from the database. Unlike before, this can be any type of node. For example, we can load the node with PK 17:

from aiida.orm import load_node
node = load_node(17)

Now, we want to find the nodes which have a direct link to this node. The node has several methods to extract this information: get_outputs(), get_outputs_dict(), get_inputs() and get_inputs_dict(). The most practical way to access this information, especially when working on the verdi shell, is by means of the inp and out attributes.

The inp attribute can be used to list and access the nodes with a direct link to node in input. The names of the input links can be printed by list(node.inp) or interactively by node.inp. + TAB. As an example, suppose that node has an input KpointsData object under the linkname kpoints. The command


returns the KpointsData object.

Similarly the out attribute can be used to display the names of links in output from node and access these nodes. Suppose that node has an output FolderData with linkname retrieved, then the command


returns the FolderData object.


For the input, there can be only one object for a given linkname. In contrast, there can be more than one output object with the same linkname. For example, a code object can be used by several calculations with the same linkname code. For this reason, we append the string _pk indicating the pk of the output code to the linkname. A linkname without _pk still exists, and refers to the oldest link.

As an example, imagine that node is a code, which is used by calculation #18 and #19. The linknames shown by node.out are

node.out.  >>
  * code
  * code_18
  * code_19

The attributes node.out.code_18 and node.out.code_19 will return two different calculation objects, and node.out.code will return the older one of the two.