{"id":127273,"date":"2022-08-14T14:11:02","date_gmt":"2022-08-14T14:11:02","guid":{"rendered":"https:\/\/blog.finxter.com\/?p=570641"},"modified":"2022-08-14T14:11:02","modified_gmt":"2022-08-14T14:11:02","slug":"how-to-append-a-new-row-to-a-csv-file-in-python","status":"publish","type":"post","link":"https:\/\/sickgaming.net\/blog\/2022\/08\/14\/how-to-append-a-new-row-to-a-csv-file-in-python\/","title":{"rendered":"How to Append a New Row to a CSV File in Python?"},"content":{"rendered":"\n
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Rate this post<\/span> <\/div>\n<\/div>\n

Python Append Row to CSV<\/h2>\n

To append a row (=dictionary<\/a>) to an existing CSV, open<\/a> the file object in append mode<\/a> using open('my_file.csv', 'a', newline='')<\/code>. Then create a csv.DictWriter()<\/code> to append a dict row using DictWriter.writerow(my_dict)<\/code>.<\/p>\n

Given the following file 'my_file.csv'<\/code>:<\/p>\n

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You can append a row (dict) to the CSV file via this code snippet:<\/p>\n

import csv # Create the dictionary (=row)\nrow = {'A':'Y1', 'B':'Y2', 'C':'Y3'} # Open the CSV file in \"append\" mode\nwith open('my_file.csv', 'a', newline='') as f: # Create a dictionary writer with the dict keys as column fieldnames writer = csv.DictWriter(f, fieldnames=row.keys()) # Append single row to CSV writer.writerow(row)\n<\/pre>\n
After running the code in the same folder as your original 'my_file.csv'<\/code>, you’ll see the following result:<\/p>\n
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Append Multiple Rows to CSV<\/h2>\n
Given the following CSV file:<\/p>\n
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To add multiple rows (i.e., dicts) to an old existing CSV file, iterate over the rows and write each row<\/code> by calling csv.DictWriter.writerow(row)<\/code> on the initially created DictWriter<\/code> object.<\/p>\n
Here’s an example (major changes highlighted):<\/p>\n
import csv # Create the dictionary (=row)\nrows = [{'A':'Z1', 'B':'Z2', 'C':'Z3'}, {'A':'ZZ1', 'B':'ZZ2', 'C':'ZZ3'}, {'A':'ZZZ1', 'B':'ZZZ2', 'C':'ZZZ3'}] # Open the CSV file in \"append\" mode\nwith open('my_file.csv', 'a', newline='') as f: # Create a dictionary writer with the dict keys as column fieldnames writer = csv.DictWriter(f, fieldnames=rows[0].keys()) # Append multiple rows to CSV for row in rows: writer.writerow(row)\n<\/pre>\n
The resulting CSV file has all three rows added to the first row:<\/p>\n
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Python Add Row to CSV Pandas<\/h2>\n
To add a row to an existing CSV using Pandas, you can set the write mode<\/code> argument to append 'a'<\/code> in the pandas DataFrame to_csv()<\/a><\/code> method like so: df.to_csv('my_csv.csv', mode='a', header=False)<\/code>.<\/p>\n
df.to_csv('my_csv.csv', mode='a', header=False)<\/pre>\n
For a full example, check out this code snippet:<\/p>\n
import pandas as pd # Create the initial CSV data\nrows = [{'A':'Z1', 'B':'Z2', 'C':'Z3'}, {'A':'ZZ1', 'B':'ZZ2', 'C':'ZZ3'}, {'A':'ZZZ1', 'B':'ZZZ2', 'C':'ZZZ3'}] # Create a DataFrame and write to CSV\ndf = pd.DataFrame(rows)\ndf.to_csv('my_file.csv', header=False, index=False) # Create another row and append row (as df) to existing CSV\nrow = [{'A':'X1', 'B':'X2', 'C':'X3'}]\ndf = pd.DataFrame(row)\ndf.to_csv('my_file.csv', mode='a', header=False, index=False)\n<\/pre>\n
The output file looks like this (new row highlighted):<\/p>\n
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Alternatively, you can open the file in append mode<\/a> using normal open()<\/a><\/code> function with the append 'a'<\/code> argument and pass it into the pandas DataFrame to_csv()<\/a><\/code> method.<\/p>\n
Here’s an example snippet for copy&paste:<\/p>\n
with open('my_csv.csv', 'a') as f: df.to_csv(f, header=False)<\/pre>\n
\"\ud83c\udf0d\" Learn More<\/strong>: If you want to learn about 7 Best Ways to Convert Dict to CSV in Python, check out this Finxter tutorial<\/a>.<\/p>\n","protected":false},"excerpt":{"rendered":"
Rate this post Python Append Row to CSV To append a row (=dictionary) to an existing CSV, open the file object in append mode using open(‘my_file.csv’, ‘a’, newline=”). Then create a csv.DictWriter() to append a dict row using DictWriter.writerow(my_dict). Given the following file ‘my_file.csv’: You can append a row (dict) to the CSV file via […]<\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[857],"tags":[73,468,528],"class_list":["post-127273","post","type-post","status-publish","format-standard","hentry","category-python-tut","tag-programming","tag-python","tag-tutorial"],"_links":{"self":[{"href":"https:\/\/sickgaming.net\/blog\/wp-json\/wp\/v2\/posts\/127273","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/sickgaming.net\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/sickgaming.net\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/sickgaming.net\/blog\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/sickgaming.net\/blog\/wp-json\/wp\/v2\/comments?post=127273"}],"version-history":[{"count":0,"href":"https:\/\/sickgaming.net\/blog\/wp-json\/wp\/v2\/posts\/127273\/revisions"}],"wp:attachment":[{"href":"https:\/\/sickgaming.net\/blog\/wp-json\/wp\/v2\/media?parent=127273"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/sickgaming.net\/blog\/wp-json\/wp\/v2\/categories?post=127273"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/sickgaming.net\/blog\/wp-json\/wp\/v2\/tags?post=127273"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}