python27从csv文件中仅提取特定列

Question

Pls excuse Im fairly new to programming trying to do something simple but cant seem to figure it out. Probably something obvious.

I need to take a huge csv file populated with about 6 columns, parse it and extract only 2 columns into a dictionary which later I will use to build and API call with a json payload. Any extra data will cause the call to fail.

I need to create a dictionary from the csv file populated with only selected columns, lets say column1 and column5 preserving the key,value structure. So far i have been able to output either only keys or only values or all keys and values but not specific key value data sets.

I need to achieve this using standard python27 the csv module , nothing extra such as panda as i have to work with what i have. I know Im missing something obvious but just cant figure it out. Help is greatly appreciated.

source file example:

column1,column2,column3,column4,column5
joe,43,888-123-4567,seattle,toyota
bill,18,888-123-4567,vancouver,gm
sally,32,888-987-1234,la,ford

desired output to dictionary:

[{'column1':'joe', 'column5':'toyota'},{'column1':'bil', 'column5':'gm'},{'column1':'sally', 'column5':'ford'}] 

code snippet:

import csv

def parseSourceFile(filename):
    filtered_data = {}
    reader = csv.DictReader(open(filename, "rb"))

    # some for loop here extracting only column1 and column5 with their values appending to filtered_data

    return result

def main():
    readerObj = parseSourceFile('somefile.csv')
    for row in readerObj:
        print row     #at this point i only want columns1,5 k,v data

if __name__ == '__main__':
    main()

Answer 1

You can store the keys you need to a list and then every row you read from csv file use dict comprehension to pick the keys you need:

import csv
import pprint

KEYS = [
    'column1',
    'column5'
]

def parseSourceFile(filename):
    with open(filename) as f:
        reader = csv.DictReader(f)
        return [{key: row[key] for key in KEYS} for row in reader]

pprint.pprint(parseSourceFile('somefile.csv'))

Output:

[{'column1': 'joe', 'column5': 'toyota'},
 {'column1': 'bill', 'column5': 'gm'},
 {'column1': 'sally', 'column5': 'ford'}]

Answer 2

What about something like

import csv

def parseSourceFile(filename):
    reader = csv.DictReader(open(filename, "r"))

    result = []
    for row in reader:
        result.append({k:v for (k,v) in row.items() if k in ['column1', 'column5']})

    return result

def main():
    result = parseSourceFile('so.csv')

    # Print what you wrote you expected
    print(result)

    # Or iterate over the list elements and print each on separate lines
    for row in result:
        print(row)

if __name__ == '__main__':
    main()

Output:

[{'column1': 'joe', 'column5': 'toyota'}, {'column1': 'bill', 'column5': 'gm'}, {'column1': 'sally', 'column5': 'ford'}]

{'column1': 'joe', 'column5': 'toyota'}
{'column1': 'bill', 'column5': 'gm'}
{'column1': 'sally', 'column5': 'ford'}