unicodecsv - read csv files

unicodecsv_sample.py

import unicodecsv

csv_file = r"C:\GIS\temp\graffiti.csv"

#read as is
with open(csv_file,"rb") as f:
    reader = unicodecsv.DictReader(f)
    reader_rows = list(reader)
print reader_rows[:3]

#[{u'OBJECTID': u'1', u'CID': u'11', u'POINT_X': u'-122.396707', u'SqFtAprox': u'5', u'FID': u'0', u'POINT_Y': u'37.7855429999'},
    #{u'OBJECTID': u'2', u'CID': u'21', u'POINT_X': u'-122.411825', u'SqFtAprox': u'6', u'FID': u'1', u'POINT_Y': u'37.7739790002'},
    #{u'OBJECTID': u'3', u'CID': u'28', u'POINT_X': u'-122.474009', u'SqFtAprox': u'4', u'FID': u'2', u'POINT_Y': u'37.7803529995'}]


#read only certain columns
fields_to_take = ['CID','POINT_X','POINT_Y']
with open(csv_file,"rb") as f:
    reader = unicodecsv.DictReader(f)
    reader_rows = list(reader)
    reader_filtered_fields = [{field:dict_row[field] for field in fields_to_take}
                              for dict_row in reader_rows]

print reader_filtered_fields[:3]

#[{'POINT_X': u'-122.396707', 'POINT_Y': u'37.7855429999', 'CID': u'11'},
    #{'POINT_X': u'-122.411825', 'POINT_Y': u'37.7739790002', 'CID': u'21'},
    #{'POINT_X': u'-122.474009', 'POINT_Y': u'37.7803529995', 'CID': u'28'}]


#write to a new csv with a query
output_file_path = r"C:\GIS\temp\graffiti_filtered.csv"
fields_to_take = ['CID','POINT_X','POINT_Y']
with open(csv_file,"rb") as f:
    reader = unicodecsv.reader(f)
    headers = [field for field in reader.next() if field in fields_to_take]
    with open(output_file_path,'ab') as output_file:
        writer = unicodecsv.writer(output_file,delimiter=',')
        writer.writerow(headers)
        for row in reader:
            if int(row[2]) > 2000:
                row_filtered = [row[2],row[4],row[5]]
                writer.writerow(row_filtered)

#three first rows of the output csv file
#CID,POINT_X,POINT_Y
#2022,-122.413350001,37.7692199998
#2093,-122.4635,37.7143009993
#2110,-122.410066,37.774991