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magicrebirth on 03/22/11

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Last Edited at 03/22/11 10:23pm

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CSV reading in python

/ Published in: Python

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# Use reader() to create a an object for reading data from a CSV file. The reader can be used as an iterator
#  to process the rows of the file in order. For example:

import csv
import sys

f = open(sys.argv[1], 'rt')
try:
    reader = csv.reader(f)
    for row in reader:
        print row
finally:
    f.close()

# the original file:

"Title 1","Title 2","Title 3"
1,"a",08/18/07
2,"b",08/19/07
3,"c",08/20/07
4,"d",08/21/07
5,"e",08/22/07
6,"f",08/23/07
7,"g",08/24/07
8,"h",08/25/07
9,"i",08/26/07

# the result:

$ python csv_reader.py testdata.csv

['Title 1', 'Title 2', 'Title 3']
['1', 'a', '08/18/07']
['2', 'b', '08/19/07']
['3', 'c', '08/20/07']
['4', 'd', '08/21/07']
['5', 'e', '08/22/07']
['6', 'f', '08/23/07']
['7', 'g', '08/24/07']
['8', 'h', '08/25/07']
['9', 'i', '08/26/07']

# In addition to working with sequences of data, the csv module includes classes for working  # with rows as dictionaries so that the fields can be named. The DictReader and DictWriter # #  classes translate rows to dictionaries instead of lists. Keys for the dictionary can be # #  passed in, or inferred from the first row in the input (when the row contains headers).

import csv
import sys

f = open(sys.argv[1], 'rt')
try:
    reader = csv.DictReader(f)
    for row in reader:
        print row
finally:
    f.close()

# returns:

$ python csv_dictreader.py testdata.csv

{'Title 1': '1', 'Title 3': '08/18/07', 'Title 2': 'a'}
{'Title 1': '2', 'Title 3': '08/19/07', 'Title 2': 'b'}
{'Title 1': '3', 'Title 3': '08/20/07', 'Title 2': 'c'}
{'Title 1': '4', 'Title 3': '08/21/07', 'Title 2': 'd'}
{'Title 1': '5', 'Title 3': '08/22/07', 'Title 2': 'e'}
{'Title 1': '6', 'Title 3': '08/23/07', 'Title 2': 'f'}
{'Title 1': '7', 'Title 3': '08/24/07', 'Title 2': 'g'}
{'Title 1': '8', 'Title 3': '08/25/07', 'Title 2': 'h'}
{'Title 1': '9', 'Title 3': '08/26/07', 'Title 2': 'i'}

URL: http://www.doughellmann.com/PyMOTW/csv/

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