from Scientific.IO.NetCDF import NetCDFFile as Dataset
import itertools as itx

frame = 2000
inputfile = 'mdcrd'


def grouper(n, iterable, fillvalue=None):
    args = [iter(iterable)] * n
    return itx.izip_longest(fillvalue=fillvalue, *args)

formatxyz = "%12.7f%12.7f%12.7f%12.7f%12.7f%12.7f"
formatxyz_size = 6
formatxyzshort = "%12.7f%12.7f%12.7f"
formatxyzshort_size = 3


ncfile = Dataset(inputfile, 'r')

variableNames = ncfile.variables.keys()
#print variableNames

shape = ncfile.variables['coordinates'].shape

'''
do the header
'''

print 'title ' + str(frame)
print "%5i%15.7e" % (shape[1],ncfile.variables['time'][frame])


'''
do the xyz coordinates
'''
xyz = ncfile.variables['coordinates'][frame]
temp = grouper(2, xyz, "")


for i in temp: 
        z = tuple(itx.chain(*i))
        if (len(z) == formatxyz_size): print formatxyz % z
        elif (len(z) == formatxyzshort_size): print formatxyzshort % z 

'''
do the velocities
'''
try:
    xyz = ncfile.variables['velocities'][frame]
    temp = grouper(2, xyz, "")

    for i in temp:  
        z = tuple(itx.chain(*i))
        if (len(z) == formatxyz_size): print formatxyz % z
        elif (len(z) == formatxyzshort_size): print formatxyzshort % z 

except(KeyError):
    
    xyz = [0] * shape[2] 
    xyz = [xyz] * shape[1]
    temp = grouper(2, xyz, "")
    
    for i in temp:
        z = tuple(itx.chain(*i))
        if (len(z) == formatxyz_size): print formatxyz % z
        elif (len(z) == formatxyzshort_size): print formatxyzshort % z 


x = ncfile.variables['cell_angles'][frame]
y = ncfile.variables['cell_lengths'][frame]
'''
do cell lengths and angles
'''
print formatxyz % tuple(itx.chain(y, x))
ncfile.close()