PythonWin2.6.5:open a text file, read it into memory, and then print each line-fails

ScottChang

Hi all,
In Python Win 2.6.5, I executed the following Python script on the attached txt file:

# open the text file, read it into memory
file = open('c:/testing/a-little-more-involved.txt').read().splitlines()
# define a new, empty list object
l = []
# iterate through the lines of the file, slice up the line by index
#   position of each data column
for line in file:
    v0 = line[0:3]
    v1 = line[3:18].strip()
    v2 = line[18:19]
    v3 = line[19:20]
    v4 = line[20:21]
    v5 = line[21:26]
    v6 = line[26:27]
    v7 = line[27:29]
    # add the parsed items to list l; as we go through the lines,
    #   we create a nested list
    l.extend([[v0,v1,v2,v3,v4,v5,v6,v7]])
# iterate through list, print out members
for each in l:
    print each

It does not work at all - no error and no output.  Please kindly help and advise me how to fix the problem.

Thanks in advance,
Scott Chang

a-little-more-involved.txt.zip

Screenshot_20250424-084938~2.png

MikeHunter

Here's a quick breakdown what the script is doing:

The "for line in file" part iterates through the lines of the text file, and assigns the name "line" to each line.
The lines like v0 = line[0:3] use Python slice notation to break up the line into pieces.  This first one assigns the first 3 characters to the name v0.  After all the slices of the line are gathered, then are appended to the list "l" as a list containing the pieces, so you end up with a bunch of lists inside a "master" list. 

Here are several good examples of using slice notation:

http://stackoverflow.com/questions/509211/good-primer-for-python-slice-notation

As far as the csv module goes, I find it very easy to use, and I highly recommend it for dealing with csv files.  You can run into a bunch of tricky situations with csv's, and the csv module will handle these for you.  Plus it's a good practice to use the standard library and not try to handle things that are already handled for you there.  I don't know of a better documentation than the official one.  But you can try Doug Hellmann's excellent site:

http://www.doughellmann.com/PyMOTW/csv/index.html#module-csv

Dealing with text files is really easy in Python.  Read about file objects here:

http://docs.python.org/2/library/stdtypes.html#file-objects

And about the opening, reading, and writing text and other kinds of files here:

http://docs.python.org/2/tutorial/inputoutput.html#reading-and-writing-files

hope this helps,
Mike