from __future__ import print_function

# REQUIREMENT:
# Count the number of times each atom name appears

#
# Open input file
#
f = open("3FX2.pdb")

#
# For each ATOM record, increment count
# for the atom name
#
counts = {}
for line in f:
	if not line.startswith("ATOM"):
		continue
	atom_name = line[12:16]
	counts[atom_name] = counts.get(atom_name, 0) + 1

#
# Close input file
#
f.close()

#
# Print number of occurrences of each atom name
#
print("Unsorted")
for atom_name, count in counts.items():
	print(atom_name, count)

#
# Print number of occurrences of each atom name
# sorted by atom name
#
print("Sorted by atom name")
for atom_name in sorted(counts.keys()):
	print(atom_name, counts[atom_name])

#
# Print number of occurrences of each atom name
# sorted by occurrence count
#
print("Sorted by occurrence count")
for count, atom_name in sorted([ (count, atom_name)
				for atom_name, count
				in counts.items() ]):
	print(atom_name, count)

#
# Print number of occurrences of each atom name
# reverse sorted by occurrence count
#
print("Reverse sorted by occurrence count")
for count, atom_name in reversed(sorted(
				[ (count, atom_name)
				for atom_name, count
				in counts.items() ])):
	print(atom_name, count)