Python read txt file as input: IndexError: list index out of range?

Question

Here is my code:

if __name__ == '__main__':
  fid = open ('200502.txt')
  data = fid.readlines()
  data = map (string.strip, data)
  x = []
  y = [] 
  da = []
  for d in data:
    s = d.split()
    x.append(float(s[0])/10000.0)
    y.append(float(s[1])/10000.0)
    da.append(float(s[2]))

When I run it I got:

Traceback (most recent call last):
  File "plot_data.py", line 286, in ?
    x.append(float(s[0])/10000.0)
IndexError: list index out of range

The 200502.txt (840kb) file is like:

1131087 224529 3.923   
1131096 224529 3.958 
1131106 224530 3.897    
1131116 224530 3.917   
1131126 224530 3.847 
(....)

wim · Accepted Answer · 2012-08-02 03:33:00Z

3

This is a fragile way to load your data. My guess is it's breaking on a newline at the end of the file, or something like that. Regardless, you should load your file with numpy.loadtxt instead (or csv module if you don't have access to numpy).

To get you started on that:

>>> import numpy
>>> data = numpy.loadtxt('/tmp/200502.txt')
>>> xs = data.T[0]/10000.
>>> ys = data.T[1]/10000.
>>> da = data.T[2]

edited Aug 2, 2012 at 3:33

answered Aug 2, 2012 at 3:26

wim

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2 Comments

Silas Ray Over a year ago

If we are getting in to questions of style, loading the x, y, and data values from each line in to separate lists is somewhat of a questionable decision to begin with. A list of objects, lists, tuples, or dicts would seem to be more sensible.

jfs Over a year ago

@sr2222: It is easy to fix: x,y,da = np.loadtxt('200502.txt', unpack=True); x *= 1e-5; y *= 1e-5

Silas Ray · Accepted Answer · 2012-08-02 03:42:01Z

0

There is at least one element in your input file that contains no data. You are iterating over data, and one of the elements is producing a 0-length list from d.split(). I'd also suggest considering loading your data in to a more structured organization. Something like loaded_data = [zip(('x', 'y', 'da'), d.split()) for d in data].

edited Aug 2, 2012 at 3:42

answered Aug 2, 2012 at 3:26

Silas Ray

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