Python IO: Reading a file using format specifier

Question

I want to read in a text file that is very poorly made in that the values in each line are sometimes not separated by spaces or commas (so i cant use .split()). I want to read it like you would in FORTRAN where I tell it exactly where each value is. This is what I am trying. Does anyone know a better approach to do this? Thanks !

f=open('f.out','r')

lines = f.readlines()

nLines = len(lines)
data = {}


keys = {'SPE':[0, 2, np.int],              #I2
      'SPEISO':[2, 3, np.int],         #I1
      'wnum':[3,15, np.float64],       #F12.6
      'S':[15, 25, np.float64],     #E10.3
      'Ecoeff':[25, 35, np.float64],     #E10.3
      'AGA':[35, 40, np.float64],     #F5.5
      'SGA':[40, 45, np.float64],     #F5.4
      'ELO':[45, 55, np.float64],     #F10.4
      'N'  :[55, 59, np.float64],     #F4.2
      'FSH':[59, 67, np.float64],     #F8.6
      'TRS':[67, 127, np.str],
      'IERR': [127, 133, np.int],
      'IEFF': [133, 145, np.str],
      'other': [145,160, np.str]  }

for k in keys:
  data[k] = np.zeros(nLines)

for i, l in enumerate(lines):
 print i
  for k in keys:
    print k
    data[[k][i]] = l.format(keys[k])

SiggyF · Accepted Answer · 2013-02-02 22:51:07Z

1

You might be able to use the read_fwf function from the pandas library.

Something like:

import pandas
pandas.read_fwf('f.out', 
   colspecs=[x[:2] for x in keys.values()],
   dtype=[x[2] for x in keys.values()]
   )

edited Feb 2, 2013 at 22:51

answered Feb 2, 2013 at 22:36

SiggyF

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2 Comments

user2036115 Over a year ago

Great! It looks like it worked. Now I just need to figure how this DataFrame object works so I can get my values into regular arrays.

SiggyF Over a year ago

You can consider the DataFrame as a number of columns, where each column represents a numpy array. You can also transform it to a numpy record array (dataframe.to_records()), but you probably want to use the nice features of the dataframe object itself.

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