[Tutor] How do I go from a textFile.txt to a list [] AND from a textFile.txt to a dictionary of dictionaries?

[Gregory Lund]

Only my second try to post to this list.
This is a dumb question with a simple (I presume) solution...
but...
how do I take a txt file with semicolon separated values and create a
dictionary and a list?
( in 2.6 because I'm working with ArcGIS.)

text file is as follows: (saved as text_data.txt) (it's longer,
this is just a sample)

ObjID;Xval;Yval;LineID;PolyID
0;1279027.0;246427.9375;0;1
1;1279069.625;246433.234375;0;1
2;1279091.0;246435.046875;1;1
3;1279112.5;246436.3125;1;1
4;1279134.0;246437.0;2;1
5;1279176.875;246436.71875;2;1
6;1279198.375;246435.734375;3;1
7;1279219.75;246434.1875;3;1

I'd like to create a list from said text data...
and a dictionary of dictionaries from said data.

Eventually I will create a point, line and polygon shapefiles from this file.
With the data above, it would be an 8 point pnt file, a 3 line line
file and 1 polygon. (point 7 connecting back to point 0)

Right now, I'm just trying to get started by creating a list and a
dictionary (to see which I want to use when creating my shapefiles.)

And, I need to do it in 2.6 because I'm working with ArcGIS.

Thanks in advance for your thoughts?
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Re: [Tutor] How do I go from a textFile.txt to a list [] AND from a textFile.txt to a dictionary of dictionaries?

[Mark Lawrence]

On 22/07/2012 23:33, Gregory Lund wrote:

Only my second try to post to this list.
This is a dumb question with a simple (I presume) solution...
but...
how do I take a txt file with semicolon separated values and create a
dictionary and a list?
( in 2.6 because I'm working with ArcGIS.)

text file is as follows: (saved as text_data.txt) (it's longer,
this is just a sample)

ObjID;Xval;Yval;LineID;PolyID
0;1279027.0;246427.9375;0;1
1;1279069.625;246433.234375;0;1
2;1279091.0;246435.046875;1;1
3;1279112.5;246436.3125;1;1
4;1279134.0;246437.0;2;1
5;1279176.875;246436.71875;2;1
6;1279198.375;246435.734375;3;1
7;1279219.75;246434.1875;3;1

I'd like to create a list from said text data...
and a dictionary of dictionaries from said data.

Eventually I will create a point, line and polygon shapefiles from this file.
With the data above, it would be an 8 point pnt file, a 3 line line
file and 1 polygon. (point 7 connecting back to point 0)

Right now, I'm just trying to get started by creating a list and a
dictionary (to see which I want to use when creating my shapefiles.)

And, I need to do it in 2.6 because I'm working with ArcGIS.

Thanks in advance for your thoughts?
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Your starter for 10 is the csv module specifically 
http://docs.python.org/library/csv.html#csv-fmt-params


--
Cheers.

Mark Lawrence.

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Re: [Tutor] How do I go from a textFile.txt to a list [] AND from a textFile.txt to a dictionary of dictionaries?

[Walter Prins]

Hi Greg,

Try this (next time try solving yourself first and post what you've
done and specific problems you're having trouble with.):

import csv

# read data using csv reader...
fileobj = open('text_data.txt')
csvreader = csv.reader(fileobj, delimiter=';')
csvreader.next() # skip header

# store lines indexed by line id in dict called polylines
# lines themselves are represented by lists.
polylines = {}

# store polygons made up of lines in dict called polygons
polygons = {}

# loop through point data from csvreader and unpack into
# dicts/lists
for line in csvreader:
#unpack lineid and polyid
lineid = line[3]
polyid = line[4]

# get the point data as list by slicing
# first entry in list is point id.
# maybe make points into a dict as well?
point = line[0:3]

# store the point in the correct line list:
# first create an empty list if needed then append
polylines[lineid] = polylines.get(lineid, [])
polylines[lineid].append(point)

# store the line in the correct polygon dict:
# first create empty dict if needed then add
# if the line not already part of the polygon.
polygons[polyid] = polygons.get(polyid, {})
if not lineid in polygons[polyid]:
polygons[polyid][lineid] = polylines[lineid]

# check the results with some pretty printing:
import pprint
pp = pprint.PrettyPrinter(indent=4)

print lines read from csv file:
pp.pprint(polylines)

print polygons read from csv file:
pp.pprint(polygons)

Walter
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