import numpy as np
import matplotlib.pyplot as plt

def read_spec ( filename ):
  with open(filename) as f:
    rec = '!'
    while rec[0] == '!': rec = f.readline()
    flds = rec.split()
    npts = abs ( int(flds[0]) )
    wno1 = float(flds[1])
    wnod = float(flds[2])
    if wnod > 0:         # regular grid
      spc = np.fromfile(f,sep=" ")
      wno = wno1 + np.arange(npts)*wnod
    else:                # irregular grid
      dat = np.fromfile(f,sep=" ").reshape(npts,2)
      wno = dat[:,0]
      spc = dat[:,1]
  return wno, spc


w,r = read_spec('tra_02000.asc')
plt.plot(w,r)
plt.title('tra_01000.asc')
plt.xlabel('Wavenumber [cm$^{-1}$]')
plt.ylabel('Transmittance')
plt.margins(x=0.0)
plt.savefig('plot.png')