AKFReader¶

The AKFReader Python class provides a convenient way to read annotated data from the binary KF files generated by AMS.

Below is an example demonstrating some of the AKFReader class’s functionality

#!/usr/bin/env amspython

from scm.akfreader import AKFReader

# ===== Load a kf file.
akf = AKFReader("test.results/dftb.rkf")


# ===== Print all content in the kf file:
akf.print_all_variables()


# ===== Read a specific variable from file.
coordinates = akf.read("Molecule%Coords")
print("Coordinates:")
print(coordinates)

# Coordinates:
# [[-1.65367945e+00  4.59827802e+00 -9.59515212e-09]
#  [ 5.88355572e-01  2.78581237e+00  1.09863437e-08]
#  ...
#  [-3.26489723e+00  3.74833282e+00  9.66428930e-01]
#  [-2.21256221e+00  5.05007997e+00 -1.93285786e+00]]


# ====== Retrieve the description, units, and additional information for a variable:
description_dict = akf.description("Molecule%Coords")
print("'Molecule%Coords' description:")
print(description_dict)

# 'Molecule%Coords' description:
# {'_type': 'float_array',
#  '_shape': [3, 'nAtoms'],
#  '_comment': 'Coordinates of the nuclei (x,y,z)',
#  '_unit': 'bohr'}


# ====== Read another variable, and do a unit conversion:
energy_in_eV = akf.read("AMSResults%Energy", units="eV")
print(f"Energy: {energy_in_eV} [eV]")

# Energy: -203.21954672148195 [eV]


# ====== Read all variables matching the pattern:
history_energies = akf.read("History%Energy(#)")
print(history_energies)

# [('History%Energy(1)', -5.758015498298242),
#  ('History%Energy(2)', -5.765039556660788),
#  ('History%Energy(3)', -5.766261662994689),
#  ('History%Energy(4)', -5.766288141072665)]

Note

The KFFile Python class can also be used to read KF files. Key differences between the AKFReader and the KFFile:

The AKFReader can provide ‘extra information’ on the content of the KF files: it can give descriptions of sections, variables, units, and automatically reshapes matrices to the proper size/shape.
The KFFile can also be used to write KF files (while the AKFReader can only read).