Update specific value from specific row with pandas python3

Question

Inside of my tag_data.csv file I want to change the column for “Posts” value from “4532” to “1234” in the the row that contains “metal “

My csv file looks like this:

    Tag    Posts
0 plastic   2456
0 paper     3449
0 metal     4532
0 other     8722

The output should be the file updated and saved to look like this:

    Tag    Posts
0 plastic   2456
0 paper     3449
0 metal     1234
0 other     8722

This is what I’ve been trying:

read_csv = pd.read_csv(‘tag_data.csv’)

read_csv.loc[read_csv.Tag == ‘metal’, ‘Posts’], [‘Posts’] = 123.to_csv(‘tag_data.csv’)

Toby Petty · Accepted Answer · 2020-02-18 01:23:33Z

1

It looks like you're trying to do too much in one line, this should do the value replacement:

read_csv.loc[(read_csv["Tag"]=="metal"), "Posts"] = 1234

Alternatively, you can use replace with a dictionary of values:

read_csv["Posts"] = read_csv["Posts"].replace({4532: 1234})

answered Feb 18, 2020 at 1:23

Toby Petty

4,6901 gold badge19 silver badges32 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Thanks for the help but for what ever reason the file does not get changed even though I can print the correct value