Convert xyz file to XDATCAR (VASP) file (**Python**)
===========
Usage: python xyz2xdat.py xyzfile  

Output: XDATCAR-lipai  

::

      import numpy as np
      import sys
      arg_num=len(sys.argv)
      if arg_num==1:
           print("no inputs!!!\n")
           exit()
      fname=sys.argv[1]
      xdat=open('XDATCAR-lipai','w')
      xyz=open(fname,'r')
      totnum=int(xyz.readline().rstrip('\n'))
      lat=xyz.readline().rstrip('\n').split('"')[1].split()[:9]
      lat=np.array([float(i) for i in lat]).reshape(3,3)
      #lat=np.mat(lat)
      
      latI=np.linalg.inv(lat)
      #print(latI)
      print("totatoms in the box: ",totnum)
      #print(lat)
      #print(latI)
      xdat.write("lipai@mail.ustc.edu.cn\n")
      xdat.write("1\n")
      xdat.write(str(lat[0,0])+' '+str(lat[0,1])+' '+str(lat[0,2])+'\n')
      xdat.write(str(lat[1,0])+' '+str(lat[1,1])+' '+str(lat[1,2])+'\n')
      xdat.write(str(lat[2,0])+' '+str(lat[2,1])+' '+str(lat[2,2])+'\n')
      ele=[]
      elnum=[]
      ele1=""
      eletype=0
      for i in range(totnum):
          a=xyz.readline().rstrip('\n').split()[0]
          if a!=ele1:
             ele.append(a)
             elnum.append(1)
             eletype+=1
             ele1=a
          else:
             elnum[eletype-1]+=1
      print("Num of element type: ",eletype)
      print(ele)
      print(elnum)
      
      for i in range(eletype):
          xdat.write(str(ele[i])+' ')
      xdat.write('\n')
      for i in range(eletype):
          xdat.write(str(elnum[i])+' ')
      xdat.write('\n')
            
      fline=0       
      while(xyz.readline()!=''):
          fline=fline+1
      
      framenum=fline/(totnum+2)+1
      print(framenum)
      
      xyz.seek(0)
      
      from math import floor
      for i in np.arange(framenum):
          xyz.readline()
          xyz.readline()
          xdat.write("Direct configuration= "+str(int(i+1))+"\n")
          for j in range(totnum):
              c=xyz.readline().rstrip('\n').split()[1:4]
              coor=np.array([float(s) for s in c])
              coorD=np.matmul(coor,latI)
              #for x in coorD:
              #    x=x-floor(x)
              #print(coorD.shape)
              xdat.write(str(coorD[0]-floor(coorD[0]))+' '+str(coorD[1]-floor(coorD[1]))+' '+str(coorD[2]-floor(coorD[2]))+'\n')