KeyError when using DictReader ()

Question

I have a number of .src files that I am trying to enter into a dictionary using DictReader (). The files look like this (only the title and the first line):

SRC V2.0.. ........Time Id Event T Conf .Northing ..Easting ...Depth Velocity .NN_Err .EE_Err .DD_Err .NE_Err .ND_Err .ED_Err Ns Nu uSt ....uMag Nt tSt ....tMag .MomMag SeiMoment ...Energy ...Es/Ep .SourceRo AspRadius .StaticSD AppStress DyStressD MaxDispla PeakVelPa PeakAccPa PSt 07-30-2010 07:43:56.543 ND 0 e 0.00 152.54 746.45 1686.31 6000 11.76 11.76 11.76 0.00 0.00 0.00 30 0 num -9.90 30 utm -3.21 -1.12 2.06e+007 2.22e+000 20.93 6.08e+000 0.00e+000 3.83e+004 1.49e+003 0.00e+000 1.52e-005 1.50e-003 0.00e+000 1 

In any case, the following code:

 import csv Time = {} Northing = {} source_file = open(NNSRC, 'rb') for line in csv.DictReader(source_file, delimiter = '\t'): Time = line['........Time'].strip() Northing = line['.Northing'].strip() print Time, Northing 

This gives me the following error:

 Traceback (most recent call last): File "C:\Python26\Lib\site-packages\xy\NNFindStages.py", line 101, in <module> Time = line['........Time'].strip() KeyError: '........Time' 

How can I explain the strange way to format the header in a file without changing the file itself?

Any help is much appreciated!

Answer 1

The title bar does not use tabs.

When I recreate your data without tabs, the line returned by the csv module contains only one (long) key. If I recreate it using real tabs, I get:

 >>> source_file = open('out.csv', 'rb') >>> reader = csv.DictReader(source_file, delimiter = '\t') >>> line = reader.next() >>> len(line) 37 >>> line.keys() ['Id', '..Easting', '.NE_Err', 'uSt', 'SeiMoment', 'MaxDispla', 'tSt', 'Ns', 'Nt', 'Nu', '.Northing', '.DD_Err', '...Energy', '....uMag', 'V2.0..', 'DyStressD', 'SRC', 'PeakAccPa', '.SourceRo', '........Time', '.EE_Err', 'T', 'Velocity', 'PeakVelPa', 'AspRadius', '...Depth', 'PSt', '....tMag', '.MomMag', 'AppStress', '...Es/Ep', '.ED_Err', 'Event', '.ND_Err', 'Conf', '.StaticSD', '.NN_Err'] >>> line['........Time'] 'ND' >>> line['.Northing'] '746.45' 

Note that values ​​do not require deletion; the module will take care of extraneous spaces for you.

You can read your header separately, clear it, and then process the rest of the data with the csv module:

 source_file = open(NNSRC, 'rb') header = source_file.readline() source_file.seek(len(header)) # reset read buffer headers = [h.strip('.') for h in header.split()] headers = ['Date'] + headers[2:] # Replace ['SRC', 'V2.0'] with a Date field instead for line in csv.DictReader(source_file, fieldnames=headers, delimiter = '\t'): # process line 

The code above reads the header line separately, splits it, and removes the extra ones . periods to execute more efficient column columns, and then sets the file for DictReader by DictReader read buffer (side is the effect of calling .seek() ).