Python – CSC

CSV Data 읽고 쓰기(Reading and Writing CSV Data)

읽기(Reading)

stocks.csv

    stocks.csv
    Symbol,Price,Date,Time,Change,Volume
    "AA",39.48,"6/11/2007","9:36am",-0.18,181800
    "AIG",71.38,"6/11/2007","9:36am",-0.15,195500
    "AXP",62.58,"6/11/2007","9:36am",-0.46,935000
    "BA",98.31,"6/11/2007","9:36am",+0.12,104800
    "C",53.08,"6/11/2007","9:36am",-0.25,360900
    "CAT",78.29,"6/11/2007","9:36am",-0.23,225400

csv library 사용

import csv
with open('stocks.csv') as f:
    f_csv = csv.reader(f)
    headers = next(f_csv)
    for row in f_csv:
        # Process row
        #print(row)
        print('basic : %s %s ' % (row[0], row[4]))

• row 는 list 자료형
• 인덱싱으로 자료 처리(indexing)
• row[0] (Symbol) and row[4] (Change).
• 인덱싱은 종종 혼동을 일으킴

namedtuple 사용

import csv
from collections import namedtuple
with open('stocks.csv') as f:
    f_csv = csv.reader(f)
    headings = next(f_csv)
    Row = namedtuple('Row', headings)
    for r in f_csv:
        row = Row(*r)
        # Process row
        #print(row)
        print('Row : %s %s ' % (row.Symbol, row.Change))

• row.Symbol and row.Change
• use of column headers

csv.DictReader 사용

import csv
with open('stocks.csv') as f:
    f_csv = csv.DictReader(f)
    for row in f_csv:
        # process row
        #print(row)
        print('OrderedDict : %s %s ' % (row['Symbol'], row['Change']))

• row['Symbol'] or row['Change'].

CSV data 쓰기 : csv.writer 사용

import csv

headers = ['Symbol','Price','Date','Time','Change','Volume']
rows = [('AA', 39.48, '6/11/2007', '9:36am', -0.18, 181800),
        ('AIG', 71.38, '6/11/2007', '9:36am', -0.15, 195500),
        ('AXP', 62.58, '6/11/2007', '9:36am', -0.46, 935000),
       ]

with open('stocks_new.csv','w', newline='') as f:
    f_csv = csv.writer(f)
    f_csv.writerow(headers)
    f_csv.writerows(rows)

쓰기(Writing)

csv.DictWriter 사용

import csv

headers = ['Symbol', 'Price', 'Date', 'Time', 'Change', 'Volume']
rows = [{'Symbol':'AA', 'Price':39.48, 'Date':'6/11/2007',
          'Time':'9:36am', 'Change':-0.18, 'Volume':181800},
        {'Symbol':'AIG', 'Price': 71.38, 'Date':'6/11/2007',
          'Time':'9:36am', 'Change':-0.15, 'Volume': 195500},
        {'Symbol':'AXP', 'Price': 62.58, 'Date':'6/11/2007',
          'Time':'9:36am', 'Change':-0.46, 'Volume': 935000},
        ]

with open('stocks_new.csv','w', newline='') as f:
    f_csv = csv.DictWriter(f, headers)
    f_csv.writeheader()
    f_csv.writerows(rows)