<put algortithm description here>
<put parameter description here>
Default: (not set)
<put parameter description here>
Options:
Default: 0
<put parameter description here>
Default: 10
<put parameter description here>
Default: 3
<put parameter description here>
Default: True
<put parameter description here>
Default: (not set)
processing.runalg('qgis:fieldcalculator', input_layer, field_name, field_type, field_length, field_precision, new_field, formula, output_layer)