CODEWITHSUNDEEP
pythoncsv
Vinni
Vinni

Reputation: 11

Change date formats in csv with Python 3

I need to exchange dateformats in a large csv from DD/MM/YYYY to YYYY-MM-DD. I have no problem printing out the values I want them to replace with, but I have a hard time actually overwriting the csv.

Here is my code:

import csv
from datetime import datetime

with open('partner_new_testteam.csv', newline='') as data:
    reader = csv.reader(data)

    for list in reader:
        for string in list:
            try:
                datetimeobject = datetime.strptime(string, '%d/%m/%Y')
                changedDate = datetimeobject.strftime('%Y-%m-%d')
                print(changedDate)

            except:
                continue

I know this code is rather sloppy, but keep in mind that I just started programming, thanks in advance!

Upvotes: 0

Views: 2057

Answers (3)

tzv
tzv

Reputation: 165

import csv
import re
from datetime import datetime

lines = []
# open file as read-only
with open('partner_new_testteam.csv', "r", newline='') as data:
    reader = csv.reader(data)
    # go over all of its rows, and the row's items and change 
    # items that match the date format
    for row in reader:
        for i, string in enumerate(row):
            if re.match(r"\d+\/\d+\/\d+", string):
                datetimeobject = datetime.strptime(string, '%d/%m/%Y')
                new_string = datetimeobject.strftime('%Y-%m-%d')
                row[i] = new_string
                print("Replaced", string, "with", new_string)
        # save edited, and originally correct ones to new list
        new_row = row
        lines.append(new_row)

# write new rows by overwriting original file
with open('partner_new_testteam.csv', "w", newline='') as data:
    writer = csv.writer(data)
    writer.writerows(lines)

Your current code does not actually change anything. You never replaced anything and you didn't open the file with write access.

You also should not use try: like it is an if. The regex matches x/x/x, where x is any amount of numbers.

Upvotes: 2

iamklaus
iamklaus

Reputation: 3770

read csv using pandas -> pd.read_csv and then use pd.to_datetime

eg. 

data = pd.DataFrame()

data['A'] = ['11/12/2018']

print(data)

            A
0  11/12/2018

using pd.to_datetime

data.A = pd.to_datetime(data['A'])

print(data)

           A
0 2018-11-12

Upvotes: 0

Lustra Loremipsum
Lustra Loremipsum

Reputation: 1

The .csv file is opened read-only per your 'open' command.

You need to pass the 'w' parameter to the 'open' command.

Upvotes: 0

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