# Is this an improvement or did I over-complicate this script for producing crystal lattices?

I'm a chemistry student working on a research team and part of my job is to produce simple computational scripts that can be understood and used by members unfamiliar with Python or other languages. I was recently tasked with producing a script for creating crystal lattices of any desired 3-dimensional permutation of AxBxC in reduced coordinates (aka fractional coordinates) using a dictionary of the primitive cell, which is essentially a minimum volume unit cell. The user sets their desired parameters, which are found in the beginning of the original script and in the userParam function of the second script, and runs the script.

Example of output:

 *******************************************************

1 x 1 x 2 PbCO3 14 supercell

x-shift: 0.000
y-shift: 0.000
z-shift: 0.000

Sorting priority: z-y-x

*******************************************************

x              y              z

1:  O   |  0.010000000 | -0.800000000 | -0.195000000
2:  Pb  | -0.251000000 | -0.574000000 | -0.113500000
3:  O   | -0.440000000 | -0.310000000 | -0.055000000
4:  O   | -0.230000000 | -0.060000000 | -0.055000000
5:  C   | -0.210000000 | -0.220000000 | -0.044000000
6:  C   |  0.210000000 |  0.220000000 |  0.044000000
7:  O   |  0.010000000 |  1.300000000 |  0.045500000
8:  O   |  0.230000000 |  0.060000000 |  0.055000000
9:  O   |  0.440000000 |  0.310000000 |  0.055000000
10:  Pb  |  0.251000000 |  0.574000000 |  0.113500000
11:  Pb  | -0.251000000 |  1.074000000 |  0.136500000
12:  O   | -0.230000000 |  0.560000000 |  0.195000000
13:  C   | -0.210000000 |  0.720000000 |  0.195000000
14:  O   | -0.010000000 |  0.800000000 |  0.195000000
15:  O   | -0.440000000 |  0.810000000 |  0.195000000
16:  O   |  0.010000000 | -0.800000000 |  0.305000000
17:  O   |  0.440000000 |  0.190000000 |  0.305000000
18:  C   |  0.210000000 |  0.280000000 |  0.305000000
19:  O   |  0.230000000 |  0.440000000 |  0.305000000
20:  Pb  |  0.251000000 | -0.074000000 |  0.363500000
21:  Pb  | -0.251000000 | -0.574000000 |  0.386500000
22:  O   | -0.440000000 | -0.310000000 |  0.445000000
23:  O   | -0.010000000 | -0.300000000 |  0.445000000
24:  O   | -0.230000000 | -0.060000000 |  0.445000000
25:  C   | -0.210000000 | -0.220000000 |  0.456000000
26:  C   |  0.210000000 |  0.220000000 |  0.544000000
27:  O   |  0.010000000 |  1.300000000 |  0.545500000
28:  O   |  0.230000000 |  0.060000000 |  0.555000000
29:  O   |  0.440000000 |  0.310000000 |  0.555000000
30:  Pb  |  0.251000000 |  0.574000000 |  0.613500000
31:  Pb  | -0.251000000 |  1.074000000 |  0.636500000
32:  O   | -0.230000000 |  0.560000000 |  0.695000000
33:  C   | -0.210000000 |  0.720000000 |  0.695000000
34:  O   | -0.010000000 |  0.800000000 |  0.695000000
35:  O   | -0.440000000 |  0.810000000 |  0.695000000
36:  O   |  0.440000000 |  0.190000000 |  0.805000000
37:  C   |  0.210000000 |  0.280000000 |  0.805000000
38:  O   |  0.230000000 |  0.440000000 |  0.805000000
39:  Pb  |  0.251000000 | -0.074000000 |  0.863500000
40:  O   | -0.010000000 | -0.300000000 |  0.945000000

***Possible inversion center found at 5-6***

Enter two numbers e.g. "10-20" corresponding to the atomic positions you would like to cleave a surface between:

1-20

O    0.010000000  -0.800000000  -0.195000000
Pb  -0.251000000  -0.574000000  -0.113500000
O   -0.440000000  -0.310000000  -0.055000000
O   -0.230000000  -0.060000000  -0.055000000
C   -0.210000000  -0.220000000  -0.044000000
C    0.210000000   0.220000000   0.044000000
O    0.010000000   1.300000000   0.045500000
O    0.230000000   0.060000000   0.055000000
O    0.440000000   0.310000000   0.055000000
Pb   0.251000000   0.574000000   0.113500000
Pb  -0.251000000   1.074000000   0.136500000
O   -0.230000000   0.560000000   0.195000000
C   -0.210000000   0.720000000   0.195000000
O   -0.010000000   0.800000000   0.195000000
O   -0.440000000   0.810000000   0.195000000
O    0.010000000  -0.800000000   0.305000000
O    0.440000000   0.190000000   0.305000000
C    0.210000000   0.280000000   0.305000000
O    0.230000000   0.440000000   0.305000000
Pb   0.251000000  -0.074000000   0.363500000

Net charge of cleaved surface: 0


Here is the original script:

#!/usr/bin/python3

x=1; y=2; z=3;

#-------------------------------------------------------------------------------------------

#enter input dictionaries here

PbCO3_14 = {

1 : ['Pb',(0.251, 0.574, 0.227)],     2 : [ 'Pb',(-0.251, 1.074, 0.273)],
3 : ['Pb',(-0.251, -0.574, -0.227)],  4 : [ 'Pb',(0.251, -0.074, 0.727)],
5 : ['C',(0.21, 0.22, 0.088)],        6 : [ 'C',(-0.21, 0.72, 0.39)],
7 : ['C',( -0.21, -0.22, -0.088)],    8 : [ 'C',(0.21, 0.28, 0.61)],
9 : ['O',(0.23, 0.06, 0.11)],        10 : [ 'O',(-0.23, 0.56, 0.39)],
11 : ['O',(-0.23, -0.06, -0.11)],     12 : [ 'O',(0.23, 0.44, 0.61)],
13 : ['O',(-0.01, 0.8, 0.39)],        14 : [ 'O',(0.01, 1.3, 0.091)],
15 : ['O',(0.01, -0.8, -0.39)],       16 : [ 'O',(-0.01, -0.30, 0.89)],
17 : ['O',( 0.44, 0.31, 0.11)],       18 : [ 'O',(-0.44, 0.81, 0.39)],
19 : ['O',(-0.44, -0.31, -0.11)],     20 : [ 'O',(0.44, 0.19, 0.61)]

}

#END OF DICTIONARIES
#*****************************************************USER-PARAMETERS*****************************************************

Name = ['PbCO3 #14'] #enter string corresponding to name of structure

output_key = ['Quantum'] #enter either 'Abinit' or 'Quantum' for desired output format of cleaved surface, default is Quantum Espresso format

#dimensions of supercell, 1x1x1 returns the primitive cell

X = 1
Y = 1
Z = 2

Sort_by = [z,y,x] #sorting priority for supercell coordinates - must be some permutation of x, y, and z

charges  = { 'H' : +1, 'Pb' : +2, 'O' : -2, 'C' : +4 }

#shifts for x y and z coordinates of the cell - use to find inversion plane

x_shift = 0
y_shift = 0
z_shift = 0

STRUCTURE = PbCO3_14 #name of input dictionary for primitive cell atoms and coordinates

#****************************************************END-OF-PARAMETERS****************************************************

def Expand(prim_cell,Atoms,prim,X,Y,Z,x_shift,y_shift,z_shift):

Atom = [ prim[1][0]/X, prim[1][1]/Y, prim[1][2]/Z ]

L_X = [ [ Atom[0] + i/X, Atom[1], Atom[2] ] for i in range(X) ];

L_XY = [ [ Coord[0], Coord[1] + i/Y, Coord[2] ] for Coord in L_X for i in range(Y) ]

L_XYZ = [ [ prim[0], round(Coord[0] + x_shift,9), round(Coord[1] + y_shift,9),
round(Coord[2] + i/Z + z_shift, 9) ] for Coord in L_XY for i in range(Z) ]

for i in range(len(L_XYZ)): Atoms =  { max( Atoms, key=int ) + 1 : L_XYZ[i], **Atoms }

return Atoms

#-------------------------------------------------------------------------------------------

def Layer(prim_cell,Atoms,Layers):

inversion = False; origin = False; k_inv = False; k_zero = False;

Layered_Atoms = sorted(Atoms.items(), key = lambda x:(x[1][Sort_by[0]],x[1][Sort_by[1]],x[1][Sort_by[2]]))

for i in range(len(Layered_Atoms)):[ Layers.update( { i + 1 : Layered_Atoms[i][1] } ) for i in range(len(Layered_Atoms)) ]

for key, value in Layers.items():

if (key != list(Layers)[-1]) and (Layers[key+1] == [ value[0],-value[1],-value[2],-value[3] ]):inversion = True; k_inv = key

if value[1] == value[2] == value[3] == 0.0: origin = True; k_zero = key

print('{:4}   {:2}     {:^12}   {:^12}   {:^12}\n'.format('','','x','y','z'))

for key, value in Layers.items():

if ((inversion == True ) and (key in [k_inv,k_inv+1])):print(fmt.inversion.format(key,*value));

if ((inversion == True) and (key not in [k_inv,k_inv+1])) or inversion == False: print(fmt.main.format(key,*value))

if inversion == True: print((color.BOLD + '\n***Possible inversion center found at {}-{}***\n' + color.END).format(k_inv,k_inv+1))

if origin == True: print('\n***Possible inversion center found at {}**\n'.format(k_zero))

return Layers

#-------------------------------------------------------------------------------------------

def Supercell(prim_cell,Atoms,Layers,X,Y,Z,x_shift,y_shift,z_shift):

for i in range(len(prim_cell)): Atoms = Expand(prim_cell,Atoms,prim_cell[i+1],*params()[1],*params()[2])

del Atoms[0]

Layers = Layer(prim_cell,Atoms,Layers)

print('\nEnter two numbers e.g. "10-20" corresponding to the atomic positions you would like to cleave a surface between')

Surface = input('\n: ').split('-');print('\n');

if Surface != [''] and (len(Surface) == 2):

[ Cleaved_Surface.update( { i + 1 : [ *Layers[i] ] } ) for i in range(int(Surface[0]),int(Surface[1])+1) ]

for i in range(len(Cleaved_Surface)):

if output_key[0] == 'Abinit':

Atom_Sort = sorted(Cleaved_Surface.items(), key = lambda x: (x[1][0],x[1][Sort_by[0]]));
print(fmt.abinit.format(Atom_Sort[i][1][1],Atom_Sort[i][1][2],Atom_Sort[i][1][3],Atom_Sort[i][1][0]))

if output_key[0] in ['','Quantum'] :

Atom_Sort = sorted(Cleaved_Surface.items(), key = lambda x: (x[1][Sort_by[0]],x[1][Sort_by[1]],x[1][Sort_by[2]]))
print(fmt.quantum.format(*Atom_Sort[i][1]))

Net_charge(charges,Cleaved_Surface)

#-------------------------------------------------------------------------------------------

def params():

Dim = [X,Y,Z]

if [(isinstance(dim,int)) for dim in Dim] != [True]*3: print('\nCheck supercell dimension parameters.\n');raise SystemExit;

Shift = [x_shift,y_shift,z_shift]

for shift in Shift:

if isinstance(shift,float) == False and shift != 0:  print('\nInvalid shift parameters.\n'); raise SystemExit

key_map = { 1: 'x', 2: 'y', 3: 'z' }; Sorter = [key_map.get(key, 'Null') for key in Sort_by]

if [Sort_by.count(sort) for sort in Sort_by] != [1]*3: print('Check Sort_by parameters.'); raise SystemExit;

if output_key[0] not in ['','Quantum','Abinit']: print('Check output_key.'); raise SystemExit

return Sorter,Dim,Shift

#-------------------------------------------------------------------------------------------

def Net_charge(charge,cleaved_surface):

net_charge = int(sum([charge.get(v[0], 'Null') for k,v in cleaved_surface.items()]));

def colorize(col,net_charge):

print(fmt.charge.format(color.BOLD,col,net_charge,color.END))

if net_charge > 0: colorize(color.GREEN,'+'+str(net_charge))

elif net_charge == 0: colorize(color.CYAN,net_charge)

else: colorize(color.RED,net_charge)

#-------------------------------------------------------------------------------------------

class color:
CYAN ='\033[96m';BOLD ='\033[1m';END ='\033[0m';HIGHLIGHT ='\033[01;97;105m';
FLASH ='\033[5m';PINK ='\033[95m';GREEN ='\033[32m';RED ='\033[31m';

class fmt:
main = '{:4}:  {:2}  | {:12.9f} | {:12.9f} | {:12.9f}';abinit = '  {:12.9f}  {:12.9f}  {:12.9f}  #{:3}';
quantum = '{:2}  {:12.9f}  {:12.9f}  {:12.9f}';charge = '\nNet charge of cleaved surface: {}{}{}{}\n';
inversion = color.HIGHLIGHT + '{:4}:  {:2}  | {:12.9f} | {:12.9f} | {:12.9f}' + color.END;

#-------------------------------------------------------------------------------------------

if __name__ == "__main__":

Atoms = { 0 : 'Null' }; Layers = {}; Cleaved_Surface = {};

if X == Y == Z == 1: print('{}\n{} unaltered cell\n'.format('\n'+'*'*55+'\n',Name[0]))
else: print('{}\n{} x {} x {} {} supercell\n'.format('\n'+'*'*55+'\n',*params()[1],Name[0]))

print('x-shift: {} \ny-shift: {} \nz-shift: {} \n\nSorting priority: {}-{}-{}\n{}'.format(*params()[2],*params()[0],'\n'+'*'*55+'\n'))
Supercell(STRUCTURE,Atoms,Layers,*params()[1],*params()[2])


I'm inexperienced at programming and wanted to teach myself about classes and basic methods by incorporating them into this script in a meaningful way, and so this is how I updated it:

#!/usr/bin/python3

def userParam(x,y,z):

#USER DICTIONARIES

PbCO3_14 = {

1 : ['Pb',(0.251, 0.574, 0.227)],     2 : [ 'Pb',(-0.251, 1.074, 0.273)],
3 : ['Pb',(-0.251, -0.574, -0.227)],  4 : [ 'Pb',(0.251, -0.074, 0.727)],
5 : ['C',(0.21, 0.22, 0.088)],        6 : [ 'C',(-0.21, 0.72, 0.39)],
7 : ['C',( -0.21, -0.22, -0.088)],    8 : [ 'C',(0.21, 0.28, 0.61)],
9 : ['O',(0.23, 0.06, 0.11)],        10 : [ 'O',(-0.23, 0.56, 0.39)],
11 : ['O',(-0.23, -0.06, -0.11)],     12 : [ 'O',(0.23, 0.44, 0.61)],
13 : ['O',(-0.01, 0.8, 0.39)],        14 : [ 'O',(0.01, 1.3, 0.091)],
15 : ['O',(0.01, -0.8, -0.39)],       16 : [ 'O',(-0.01, -0.30, 0.89)],
17 : ['O',( 0.44, 0.31, 0.11)],       18 : [ 'O',(-0.44, 0.81, 0.39)],
19 : ['O',(-0.44, -0.31, -0.11)],     20 : [ 'O',(0.44, 0.19, 0.61)]

}

#END OF DICTIONARIES

#*****************************************************USER-PARAMETERS*****************************************************

STRUCTURE = PbCO3_14 # name of input dictionary for primitive cell atoms and coordinates

Name = ['PbCO3 #14'] # enter string corresponding to name of structure

# dimensions of supercell, 1x1x1 returns the primitive cell

X = 1
Y = 1
Z = 2

sortBy = [z,y,x] #sorting priority for supercell coordinates - must be some permutation of x, y, and z

charges  = { 'H' : +1, 'Pb' : +2, 'O' : -2, 'C' : +4 }

# shifts for x y and z coordinates of the cell - use to find inversion plane

x_shift = 0
y_shift = 0
z_shift = 0

outputKey = ['Quantum'] # enter either 'Abinit' or 'Quantum' for desired output format of cleaved surface, default is Quantum Espresso format

#****************************************************END-OF-PARAMETERS****************************************************

return [STRUCTURE,Name,outputKey,[X,Y,Z],sortBy,[x_shift,y_shift,z_shift],charges]

#-------------------------------------------------------------------------------------------

class color:
CYAN ='\033[96m';BOLD ='\033[1m';END ='\033[0m';HIGHLIGHT ='\033[01;97;105m';
FLASH ='\033[5m';PINK ='\033[95m';GREEN ='\033[32m';RED ='\033[31m';

class fmt:
main = '{:4}:  {:2}  | {:12.9f} | {:12.9f} | {:12.9f}';
abinit = '  {:12.9f}  {:12.9f}  {:12.9f}  #{:3}';
quantum = '{:2}  {:12.9f}  {:12.9f}  {:12.9f}';
charge = '\nNet charge of cleaved surface: {}{}{}{}\n';
inversion = color.HIGHLIGHT + '{:4}:  {:2}  | {:12.9f} | {:12.9f} | {:12.9f}' + color.END;
header = '{:4}   {:2}     {:^12}   {:^12}   {:^12}\n'
showParam = 'x-shift: {:4.3f} \ny-shift: {:4.3f} \nz-shift: {:4.3f} \n\nSorting priority: {}-{}-{}\n{}'

class Supercell:

def __init__(self,structure,name,outputKey,dim,sortBy,shift,charges):

self.primitive = structure;
self.name = name[0]
self.format = outputKey[0]
self.sortBy = sortBy
self.dim = dim
self.X = dim[0]; self.Y = dim[1]; self.Z = dim[2];
self.shift = shift
self.x_shift = shift[0]; self.y_shift = shift[1]; self.z_shift = shift[2]
self.charges = charges
self.inversion = False; self.inversionKey = False
self.origin = False; self.zeroKey = False
self.layers = {}
self.cleaved = {}

#-------------------------------------------------------------------------------------------

def checkParam(self):

if [(isinstance(dim,int)) for dim in self.dim] != [True]*3: print('\nCheck supercell dimension parameters.\n');raise SystemExit;
for shift in self.shift:
if isinstance(shift,float) == False and shift != 0:  print('\nInvalid shift parameters.\n'); raise SystemExit
if [self.sortBy.count(sort) for sort in self.sortBy] != [1]*3: print('Check sortBy parameters.'); raise SystemExit;

keyMap = { 1: 'x', 2: 'y', 3: 'z' }; sortKeys = [keyMap.get(key, 'Null') for key in self.sortBy]

if self.format not in ['','Quantum','Abinit']: print('Check outputKey.'); raise SystemExit

return sortKeys

#-------------------------------------------------------------------------------------------

def constructCell(self):

emptyCell = { 0 : 'Null' }

for i in range(len(self.primitive)):

atom = self.primitive[i+1][0]

basis = [ self.primitive[i+1][1][0]/self.X, self.primitive[i+1][1][1]/self.Y, self.primitive[i+1][1][2]/self.Z ]

X_RED = [ [ basis[0] + i/self.X, basis[1], basis[2] ] for i in range(self.X) ];

XY_RED = [ [ xred[0], xred[1] + i/self.Y, xred[2] ] for xred in X_RED for i in range(self.Y) ]

XYZ_RED = [ [ atom, round(xred[0] + self.x_shift,9), round(xred[1] + self.y_shift,9), round(xred[2] + i/self.Z + self.z_shift, 9) ] for xred in XY_RED for i in range(self.Z) ]

for i in range(len(XYZ_RED)): emptyCell =  { max( emptyCell, key=int ) + 1 : XYZ_RED[i], **emptyCell }

del emptyCell[0]; return emptyCell

#-------------------------------------------------------------------------------------------

def layerCell(self):

cell = self.constructCell()

layeredCell = sorted(cell.items(), key = lambda x:(x[1][self.sortBy[0]],x[1][self.sortBy[1]],x[1][self.sortBy[2]]))

for i in range(len(layeredCell)):[ self.layers.update( { i + 1 : layeredCell[i][1] } ) for i in range(len(layeredCell)) ]

return self.layers

#-------------------------------------------------------------------------------------------

def displayParam(self):

sortKeys = self.checkParam()

if self.X == self.Y == self.Z == 1: print('{}\n{} unaltered cell\n'.format('\n'+'*'*55+'\n',self.name))

else: print('{}\n{} x {} x {} {} supercell\n'.format('\n'+'*'*55+'\n',*self.dim,self.name))

print(fmt.showParam.format(*self.shift,*sortKeys,'\n'+'*'*55+'\n'))

#-------------------------------------------------------------------------------------------

def displayCell(self):

self.displayParam()

layers = self.layerCell()

for key, value in layers.items():

if (key != list(layers)[-1]) and (layers[key+1] == [value[0],-value[1],-value[2],-value[3]]): self.inversion = True; self.inversionKey = key
if value[1] == value[2] == value[3] == 0.0: self.origin = True; self.zeroKey = key

for key, value in layers.items():

if ((self.inversion == True ) and (key in [self.inversionKey,self.inversionKey+1])):print(fmt.inversion.format(key,*value));
if ((self.inversion == True) and (key not in [self.inversionKey,self.inversionKey+1])) or self.inversion == False: print(fmt.main.format(key,*value))

if self.inversion == True: print((color.BOLD + '\n***Possible inversion center found at {}-{}***\n' + color.END).format(self.inversionKey,self.inversionKey+1))
if self.origin == True: print('\n***Possible inversion center found at {}**\n'.format(self.zeroKey))

while True:

Surface = input('\nEnter two numbers e.g. "10-20" corresponding to the atomic positions you would like to cleave a surface between:\n\n').split('-');print('\n')

if Surface != [''] and (len(Surface) == 2):

[ self.cleaved.update( { i + 1 : [ *layers[i] ] } ) for i in range(int(Surface[0]),int(Surface[1])+1) ]

else: print('Exiting...\n'); raise SystemExit

for i in range(len(self.cleaved)):

if self.format == 'Abinit':

cellSort = sorted(self.cleaved.items(), key = lambda x: (x[1][0],x[1][self.sortBy[0]]));
print(fmt.abinit.format(cellSort[i][1][1],cellSort[i][1][2],cellSort[i][1][3],cellSort[i][1][0]))

if self.format in ['','Quantum']:

cellSort = sorted(self.cleaved.items(), key = lambda x: (x[1][self.sortBy[0]],x[1][self.sortBy[1]],x[1][self.sortBy[2]]))
print(fmt.quantum.format(*cellSort[i][1]))

netCharge = int(sum([self.charges.get(data[0], 'Null') for data in self.cleaved.values()]));

if netCharge > 0: print(fmt.charge.format(color.BOLD,color.GREEN,'+'+str(netCharge),color.END))
elif netCharge == 0: print(fmt.charge.format(color.BOLD,color.CYAN,netCharge,color.END))
else: print(fmt.charge.format(color.BOLD,color.RED,netCharge,color.END))

print('Press enter to exit')

self.cleaved = {}

#-------------------------------------------------------------------------------------------

if __name__ == "__main__":

Supercell(*userParam(1,2,3)).displayCell()


Standard input techniques. Do not design a process that will require users to edit your Python code. It will be a hassle for you – at a minimum. If a program needs information from users, use one or more of the standard methods: (1) command-line arguments (eg argparse); (2) a JSON, YAML, or some other type of configuration file that either resides in a default location for the user or that the user supplies, via a path, on the command line; and (3) only as a last resort, real-time input() (avoid, avoid, avoid, if you can).

Compute or print. If possible, reorganize your code to make it more testable. Highly algorithmic functions or methods should not print or get user input, both of which make testing harder and more annoying. Rather, they should take data as input and return data as output. Do the printing and user-interacting in the "outer shell" of your program, not its algorithmic guts.

Functions. Don't put substantive code in the __name__ conditional. It's not testable, extensible, or flexible going forward. Putting all code in functions/methods is a great idea that has survived the test of time: do it and you'll be standing on the shoulders of giants!

# No.

if __name__ == "__main__":
Supercell(*userParam(1,2,3)).displayCell()

# Yes.

import sys

def main(args):
nums = [int(a) for a in args] or [1, 2, 3]
Supercell(*userParam(*nums)).displayCell()

if __name__ == '__main__':
main(sys.argv[1:])


Readability. Pay a lot more attention to code readability and scanability. You might have to maintain this beast in the future. I promise that you will forget – much more quickly and thoroughly than you expect in your youth – how it works. Here's a purely stylistic edit of one function with that in mind:

def constructCell(self):
# Blah, blah, blah.
emptyCell = {0: 'Null'}

# Blah, blah, blah.
# Organize your code in commented paragraphs.
# Blank lines between meaningful paragraphs, but not within them.
for i in range(len(self.primitive)):

# Use convenience variables to reduce repetition and the code's visual mass.
prim1 = self.primitive[i + 1]
atom = prim1[0]

# Prefer "more short lines" over "fewer long lines". Among other
# things, this approach allows readers to understand logical structure
# and perceive similarities, differences, and errors more readily.
# Also, let your operators breathe.
basis = [
prim1[1][0] / self.X,
prim1[1][1] / self.Y,
prim1[1][2] / self.Z, # Include terminal comma for better maintainability.
]

# Organize long list/dict comprehensions like a data structure to
# convey the logical hierarchy. One could argue that the inner comprehensions
# for X_RED and XY_RED could be put into a single line. Perhaps, but
# I would rather maintain the code in this fully multi-line format.
X_RED = [
[
basis[0] + i / self.X,
basis[1],
basis[2],
]
for i in range(self.X)
]
XY_RED = [
[
xred[0],
xred[1] + i / self.Y,
xred[2],
]
for xred in X_RED
for i in range(self.Y)
]
XYZ_RED = [
[
atom,
round(xred[0] + self.x_shift, 9),
round(xred[1] + self.y_shift, 9),
round(xred[2] + i / self.Z + self.z_shift, 9),
]
for xred in XY_RED for i in range(self.Z)
]

for i in range(len(XYZ_RED)):
emptyCell = {
max(emptyCell, key = int) + 1: XYZ_RED[i],
**emptyCell,
}

del emptyCell[0];
return emptyCell


Puzzling data structure. Why is self.primitive a dict with keys 1..20 rather than just a list of 20 things? There could be an excellent reason (I don't know chemistry), but it seems an odd choice on the surface.

Response to OP's question about how to get large-ish user inputs for a Python script:

In my experience working with a lot of technically-minded non-programmers (chemists in your case, social scientists in mine), people almost never have problems reading and editing pretty-printed JSON files. YAML has some nice features (aesthetically better, less line noise, files can include comments), but it also includes some edge-case gotchas that can trip people up if the data contains a wider range of characters. If your data is simple (the primitive cells look like nothing more than ASCII and numbers), YAML could be nice for the aesthetics. But JSON is more edge-case-proof. Either one would be a reasonable choice.

Either way, a few approaches come to mind, depending on work process details. (1) A shared, team-wide file is some known location. Users can add their primitive definitions in that file. This requires that team members not edit the file at the same time or use some other coordination mechanism, such as a Git or an equivalent. (2) Each user has their own JSON file, in a default location like \$HOME/magic-crystals/primitives.json or whatever. (3) Primitive definitions are stored in the script itself, and you control which ones get added, based on the team's input.

Those approaches are not mutually exclusive and can be combined in various ways (but start simple). Once the primitive file(s) are in place, users can provide the needed inputs, including a primitive name like PbCO3_14, directly on the command-line and, only if truly necessary, via input(). If you write and maintain enough command-line scripts, you will growth to hate input() -- truly, a source of much evil and computer-science mis-education.

• Thanks for pointing all these issues out. My goal is to become a competent coder and these are the things I need to hear. This script is a part of a series of modules I've written and I use the self.primitive dictionary format universally. A list would have probably been a better choice, but I would have to gut some other modules to reintegrate everything.
– R.T
Aug 30 '20 at 14:10
• The other team members need to add their own primitive cell which could be of length 4 or 100. What would be an effective way to allow users to enter large primitive cells, even if it's not in dictionary format?
– R.T
Aug 30 '20 at 14:46
• @R.T I added a reply to your follow-up question. I don't know if it truly addresses what you're asking, but it might give you some options to consider.
– FMc
Aug 30 '20 at 18:14

Unfortunately, I know nothing of crystal lattices, so I won't be able to touch on any aspect of them.

And it seems from your phrasing that you wrote all of the code here. I'm also not well versed in OOP, and I rarely use classes, so I'll just comment on what I can in the code shown here.

I consider your spacing and indentation in general to be off.

Things like:

PbCO3_14 = {

. . .

}


PEP8 says that the closing brace should either be flush to the left, or in-line with the first piece of data from the left. It doesn't recommend lining up with the opening brace.

You also have an odd mix of far too much spacing in some places, and not enough spacing in others. For example, your first part of that same dictionary looks like:

PbCO3_14 = {

1 : ['Pb',(0.251, 0.574, 0.227)],     2 : [ 'Pb',(-0.251, 1.074, 0.273)],
. . .


I don't think that initial empty line is helping readability. Also, I wouldn't put multiple keys on one line. If you're searching for a certain key, you now need to look over two columns, once you realize that it's spread out over two columns. It's longer as one column, but there are other ways around that.

Your entire Layer function is also a good example of too much spacing. Having an extra empty line between every line of code doesn't help readability. Empty lines should be used to group like-code together. Spacing everything out just forces your reader to scroll more to see code, and contributes to preventing the whole function from fitting on the screen at once.

Then at the opposite end of the spectrum, you have lines like:

def Expand(prim_cell,Atoms,prim,X,Y,Z,x_shift,y_shift,z_shift):


Where you have no spacing between parameters. In general, commas should be followed by a space if anything else comes after the comma. Smooshing everything together just makes it more difficult to tell the parameters apart at a glance.

This is also far too compressed:

class color:
CYAN ='\033[96m';BOLD ='\033[1m';END ='\033[0m';HIGHLIGHT ='\033[01;97;105m';
FLASH ='\033[5m';PINK ='\033[95m';GREEN ='\033[32m';RED ='\033[31m';


Each member should be on its own line. You're also inconsistent with spacing around =. You have a space on the left, but no space on the right.

Also on lines like this:

L_X = [ [ Atom[0] + i/X, Atom[1], Atom[2] ] for i in range(X) ];


x=1; y=2; z=3;


Please don't do this. In almost every language and style guide, multiple declarations on a single line are discouraged. It generally makes it more difficult to find the source of a variable while scanning over the file. Each "declaration" should be on its own line, and without semicolons (semicolons are very rarely used in Python). You're using semicolons all over, even though they're unnecessary. In every case I can see in this code, semicolons are just adding noise to the lines. Don't use them like you would in Java or C++.

Names should be in "snake_case": lowercase, separated by underscores. Uppercase is reserved for things like class names, which are in "UpperCamelCase".

 for i in range(len(L_XYZ)): Atoms =  { max( Atoms


Putting an entire for loop on a single line is not a good idea. Trying to force everything on to a single line just forces your users to scroll left and right to read your code. Code that is shorter vertically is not necessarily more readable if that bulk was just moved across horizontally.

Your color class (which should be Color) is defining an enum; a closed set of options to be chosen from. Python has a built-in for that that adds some extra features:

from enum import Enum

. . .

class Color(Enum):
CYAN = '\033[96m'
BOLD = '\033[1m'
END = '\033[0m'
HIGHLIGHT = '\033[01;97;105m'
FLASH = '\033[5m'
PINK = '\033[95m'
GREEN = '\033[32m'
RED = '\033[31m'


You likely don't need any of its special features, but by having the class inherit from Enum, you're indicating to your reader that that's what the intent of the class is. That could be inferred, but explicit is always good.

I'd also consider renaming that class to AnsiiCodes or something. You have elements in there line END and FLASH that aren't themselves colors.

In a few places you're using a list as a tuple:

Atom = [ prim[1][0]/X, prim[1][1]/Y, prim[1][2]/Z ]


Lists are for when you want to be able to alter the structure later. You're only using it as a read-only storage container though, so a tuple would be better:

atom = (prim[1][0]/X, prim[1][1]/Y, prim[1][2]/Z)
# or even
atom = prim[1][0]/X, prim[1][1]/Y, prim[1][2]/Z  # Parenthesis aren't necessary, although I'd still use them here


Tuples are generally faster and require less memory than lists. Again, they also indicate intent, which is important.

In a few places you compare agains't True/False:

if isinstance(shift,float) == False
if ((inversion == True )
or inversion == False:


That's not necessary though. == already evaluates to a True/False, so comparing against them again is redundant. A line like:

if ((inversion == True) and (key not in [k_inv,k_inv+1])) or inversion == False:


Would be better written as:

if (inversion and (key not in [k_inv,k_inv+1])) or not inversion:


I'd have to double check precedence, but I believe all those parenthesis are superfluous as well.

# Summary

• Use less empty lines.
• Don't try to shove multiple independent things onto a single line.
• Don't use semicolons where they aren't necessary (and the places they are necessary should usually be rewritten anyways).
• Abide by proper naming standards
• Thanks for such a thorough and descriptive critique. I've only just started coding in the last 6 months so now is the time to establish better practices.
– R.T
Aug 30 '20 at 14:24