Python csv append to existing row

For appending a new row to an existing CSV file we have many ways to do that. Here we will discuss 2 ways to perform this task effectively. So, we have 2 ways first is ‘Append a list as a new row to the existing CSV file’ and the second way is ‘Append a dictionary as a new row to the existing CSV file’.

First, let’s have a look at our existing CSV file contents. Suppose we have CSV file event.csv which has the below contents.

CSV file before append

For writing a CSV file, the CSV module provides two different classes writer and Dictwriter.

Append a list as a new row to the existing CSV file

let’s see how to use writer class to append a list as a new row into an existing CSV file. There are several steps to take that.

• Import writer class from csv module
• Open your existing CSV file in append mode
  Create a file object for this file.
• Pass this file object to csv.writer() and get a writer object.
• Pass the list as an argument into the writerow() function of the writer object.
  (It will add a list as a new row into the CSV file).
• Close the file object

Let’s take one List that we want to add as a new row.

List=[6,'William',5532,1,'UAE']

Now apply the above steps to the program.

Python3

from csv import writer

List=[6,'William',5532,1,'UAE']

with open('event.csv', 'a') as f_object:

    writer_object = writer(f_object)

    writer_object.writerow(List)

    f_object.close()

Output:

CSV file After appending List

When you are executing this program Ensure that your CSV file must be closed otherwise this program will give you a permission error.

Append a dictionary as a new row to the existing CSV file

let’s see how to use DictWriter class to append a dictionary as a new row into an existing CSV file. There are several steps to do that.

• Import DictWriter class from CSV module.
• Open your CSV file in append mode
  Create a file object for this file.
• Pass the file object and a list of column names to DictWriter()
  You will get a object of DictWriter.
• Pass the dictionary as an argument to the Writerow() function of DictWriter
  (it will add a new row to CSV file).
• Close the file object

Let’s take one Dictionary that we want to add as a new row.

dict={'ID':6,'NAME':'William','RANK':5532,'ARTICLE':1,'COUNTRY':'UAE'}

Now apply the above steps to the program.

Python3

from csv import DictWriter

field_names = ['ID','NAME','RANK',

               'ARTICLE','COUNTRY']

dict={'ID':6,'NAME':'William','RANK':5532,

      'ARTICLE':1,'COUNTRY':'UAE'}

with open('event.csv', 'a') as f_object:

    dictwriter_object = DictWriter(f_object, fieldnames=field_names)

    dictwriter_object.writerow(dict)

    f_object.close()

Output:

CSV file after Appending Dictionary

When you are executing this program ensures that your CSV file must be closed otherwise this program will give you a permission error.

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