How To Append Data In Python

When working with data in Python, you often need to append new items to existing data structures, such as lists, dictionaries, or data files. In this tutorial, we will explore several methods to append data in Python, including appending to lists, and dictionaries, and appending data to files.

Step 1: Appending data to a list

A list is a mutable, ordered Python data structure that can hold items of various data types. You can use the append() method to add new items to the end of a list.

Here’s an example:

fruits = ['apple', 'banana', 'cherry']

fruits.append('orange')

print(fruits)

This code will produce the following output:

['apple', 'banana', 'cherry', 'orange']

Step 2: Appending data to a dictionary

A dictionary is another Python data structure that stores key-value pairs. To append data to a dictionary, you can assign a new value to a new key, or use the update() method.

Here’s an example of both methods:

user = {'name': 'John', 'age': 30}

user['gender'] = 'male'

user.update({'city': 'New York'})

print(user)

This code will produce the following output:

{'name': 'John', 'age': 30, 'gender': 'male', 'city': 'New York'}

Step 3: Appending data to a text file

To append data to a text file, you can use the built-in open() function with the mode set to ‘a’ (for ‘append’). This will enable you to write data to the file without overwriting its existing content.

Here’s an example:

1 2	with open('example.txt', 'a') as file: file.write('\nThis line will be appended to the file.')

This code will append the following line to the “example.txt” file:

This line will be appended to the file.

If the file does not exist, it will be created with the appended line.

Step 4: Appending data to a CSV file

Comma Separated Values (CSV) files are a common data exchange format that can be easily read and processed by Python. To append data to a CSV file, you can use the csv module that comes with Python.

Here’s an example of appending a new row to a CSV file:

import csv

row = ['John', 'Doe', '30', 'New York']

with open('example.csv', 'a', newline='') as csvfile:

writer = csv.writer(csvfile)

writer.writerow(row)

This code will append the given row to the “example.csv” file:

John,Doe,30,New York

If the file does not exist, it will be created with the appended row.

Full code

# Appending to a list

fruits = ['apple', 'banana', 'cherry']

fruits.append('orange')

print(fruits)

# Appending to a dictionary

user = {'name': 'John', 'age': 30}

user['gender'] = 'male'

user.update({'city': 'New York'})

print(user)

# Appending to a text file

with open('example.txt', 'a') as file:

file.write('\nThis line will be appended to the file.')

# Appending to a CSV file