I found that reading a single column file with strings is not that easy in python.

When I want the following function to read each line of the file provided and do what I want it returns an empty data frame. If I call the function with number of lines of the file – 1 then it returns the data frame with data, but I lose the last line.

def xToy(fname, typ, nlines):
   i = 0
   x1 = [None] * nlines
   x2 = [None] * nlines
   x3 = [None] * nlines
   dfm = pd.DtaFrame({'xSrt': x1, 'ySrt': x2, 'typ': x3})
   with open(fname, 'r') as read_obj:
      lines = read_obj.readlines()
      for line in lines:
         if i < nlines - 1 :
            line = line.strip()
            y = yfromx(line)
            x1[i] = line
            x2[i] = y
            x3[i] = typ
         else:
            dfm['xSrt'] = x1
            dfm['ySrt'] = x2
            dfm['typ'] = x3
            return dfm
         i += 1

If I call the function with actual number of lines (112) in the file

dp = xToy("file.xyz", 1, 112)

and then if I do the following, I get “none”

print(dp)

if I call the function with number of lines in the file – 1

dp = xToy("file.xyz", 1, 111)

then

print(dp) 

shows data in dp.

This means my function fails to process the last line of the file and if I provide number of lines -1 as nlines then I get the data, but I lose the last line.

To address this issue, I did the following and it works

def xToy(fname, typ, nlines):
   i = 0
   x1 = [None] * nlines
   x2 = [None] * nlines
   x3 = [None] * nlines
   dfm = pd.DtaFrame({'xSrt': x1, 'ySrt': x2, 'typ': x3})
   with open(fname, 'r') as read_obj:
      lines = read_obj.readlines()
      for line in lines:
         if i < nlines - 1 :
            line = line.strip()
            y = yfromx(line)
            x1[i] = line
            x2[i] = y
            x3[i] = typ
         else:
            line = line.strip()
            y = yfromx(line)
            x1[i] = line
            x2[i] = y
            x3[i] = typ
            dfm['xSrt'] = x1
            dfm['ySrt'] = x2
            dfm['typ'] = x3
            return dfm
         i += 1

Is there a smart way to do the same?

Yes, as mkrieger1 pointed out, I failed to spot that my return was inside the for loop. If I bring my return out as shown below, everything works as expected.

def xToy(fname, typ, nlines):
   i = 0
   x1 = [None] * nlines
   x2 = [None] * nlines
   x3 = [None] * nlines
   dfm = pd.DtaFrame({'xSrt': x1, 'ySrt': x2, 'typ': x3})
   with open(fname, 'r') as read_obj:
      lines = read_obj.readlines()
      for line in lines:
         if i < nlines - 1 :
            line = line.strip()
            y = yfromx(line)
            x1[i] = line
            x2[i] = y
            x3[i] = typ
         else:
            dfm['xSrt'] = x1
            dfm['ySrt'] = x2
            dfm['typ'] = x3
         i += 1
      return dfm