How To Read And Write Files Using Python : A Beginner’s Guide With Examples

In this article, we'll take a look at Hide

1) Different modes for opening a file

2) Working with .txt Files

2.1) Reading a .txt File (General Way)

2.2) Standard Way to Read .txt files

2.3) Writing to a .txt File

3) Working with .csv Files, everything will be merged

3.1) Reading a .csv File

3.2) Writing to a .csv File

4) Working with .json Files

4.1) Reading a .json File

4.2) Writing to a .json File

5) Working with .json Files Using pandas

5.1) Writing to a .json File

5.2) Conclusion

Working with files is common in many Python applications, especially in data processing, configuration management, and logging. Python offers built-in libraries and modules that make it straightforward to handle various file formats, such as .txt, .csv, and .json. In this article, we’ll explore how to read and write files using Python.

Different modes for opening a file

In Python, when we open a file using the open() function, we must specify the mode we want to which specifies what we want to do with the file. Here are the common modes available:

Mode	Description	Behavior
`r`	Read-only mode.	Opens the file for reading. File must exist; otherwise, it raises an error.
`rb`	Read-only in binary mode.	Opens the file for reading binary data. File must exist; otherwise, it raises an error.
`r+`	Read and write mode.	Opens the file for both reading and writing. File must exist; otherwise, it raises an error.
`rb+`	Read and write in binary mode.	Opens the file for both reading and writing binary data. File must exist; otherwise, it raises an error.
`w`	Write mode.	Opens the file for writing. Creates a new file or truncates the existing file.
`wb`	Write in binary mode.	Opens the file for writing binary data. Creates a new file or truncates the existing file.
`w+`	Write and read mode.	Opens the file for both writing and reading. Creates a new file or truncates the existing file.
`wb+`	Write and read in binary mode.	Opens the file for both writing and reading binary data. Creates a new file or truncates the existing file.
`a`	Append mode.	Opens the file for appending data. Creates a new file if it doesn’t exist.
`ab`	Append in binary mode.	Opens the file for appending binary data. Creates a new file if it doesn’t exist.
`a+`	Append and read mode.	Opens the file for appending and reading. Creates a new file if it doesn’t exist.
`ab+`	Append and read in binary mode.	Opens the file for appending and reading binary data. Creates a new file if it doesn’t exist.
`x`	Exclusive creation mode.	Creates a new file. Raises an error if the file already exists.
`xb`	Exclusive creation in binary mode.	Creates a new binary file. Raises an error if the file already exists.
`x+`	Exclusive creation with read and write mode.	Creates a new file for reading and writing. Raises an error if the file exists.
`xb+`	Exclusive creation with read and write in binary mode.	Creates a new binary file for reading and writing. Raises an error if the file exists.

Working with `.txt` Files

Text files are the simplest form of files used for storing unstructured or lightly structured data.

Reading a `.txt` File (General Way)

# general way to read text file

file = open('example.txt','r') # r for file read
content = file.read()
print(content)

file.close()

# general way to read text file

file = open('example.txt','r') # r for file read

content = file.read()

print(content)

file.close()

Standard Way to Read .txt files

# Open and read a text file
with open('example.txt', 'r') as file:
    content = file.read()
    print(content)

# Open and read a text file

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

content = file.read()

print(content)

Writing to a `.txt` File

# Write to a text file (overwrite if exists)
with open('example.txt', 'w') as file:
    file.write("This is a new line of text.\nAnother line here.")

# Append to a text file
with open('example.txt', 'a') as file:
    file.write("\nAppended line of text.")

# Write to a text file (overwrite if exists)

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

file.write("This is a new line of text.\nAnother line here.")

# Append to a text file

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

file.write("\nAppended line of text.")

Working with `.csv` Files, everything will be merged

CSV (Comma-Separated Values) files are used to store tabular data. Python provides a built-in A csv module for reading and writing such files.

Reading a `.csv` File

import csv

# Read CSV into list of rows
with open('data.csv', newline='') as csvfile:
    reader = csv.reader(csvfile)
    for row in reader:
        print(row)

import csv

# Read CSV into list of rows

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

reader = csv.reader(csvfile)

for row in reader:

print(row)

Writing to a `.csv` File

import csv

# Write list of rows to a CSV file
data = [
    ['Name', 'Age', 'City'],
    ['Alice', 30, 'New York'],
    ['Bob', 25, 'Los Angeles']
]

with open('output.csv', 'w', newline='') as csvfile:
    writer = csv.writer(csvfile)
    writer.writerows(data)

import csv

# Write list of rows to a CSV file

data = [

['Name', 'Age', 'City'],

['Alice', 30, 'New York'],

['Bob', 25, 'Los Angeles']

]

with open('output.csv', 'w', newline='') as csvfile:

writer = csv.writer(csvfile)

writer.writerows(data)

Working with `.json` Files

JSON (JavaScript Object Notation) is commonly used for storing structured data. Python’s json module provides methods for parsing and writing JSON data.

Reading a `.json` File

import json

# Load JSON from a file
with open('data.json', 'r') as json_file:
    data = json.load(json_file)
    print(data)

import json

# Load JSON from a file

with open('data.json', 'r') as json_file:

data = json.load(json_file)

print(data)

Writing to a `.json` File

import json

# Write dictionary to a JSON file
person = {
    "name": "Alice",
    "age": 30,
    "city": "New York"
}

with open('output.json', 'w') as json_file:
    json.dump(person, json_file, indent=4)

import json

# Write dictionary to a JSON file

person = {

"name": "Alice",

"age": 30,

"city": "New York"

}

with open('output.json', 'w') as json_file:

json.dump(person, json_file, indent=4)

Working with `.json` Files Using `pandas`

The the pandas library is widely used for data analysis and makes reading and writing JSON files especially simple, particularly when the data is structured like a table (i.e., records or arrays of dictionaries).

import pandas as pd

# Read JSON file into a DataFrame
df = pd.read_json('data.json')

# Display the DataFrame
print(df)

import pandas as pd

# Read JSON file into a DataFrame

df = pd.read_json('data.json')

# Display the DataFrame

print(df)

Writing to a `.json` File

import pandas as pd

# Create a sample DataFrame
data = {
    "name": ["Alice", "Bob"],
    "age": [30, 25],
    "city": ["New York", "Los Angeles"]
}
df = pd.DataFrame(data)

# Write DataFrame to a JSON file
df.to_json('output.json', orient='records', indent=4)

import pandas as pd

# Create a sample DataFrame

data = {

"name": ["Alice", "Bob"],

"age": [30, 25],

"city": ["New York", "Los Angeles"]

}

df = pd.DataFrame(data)

# Write DataFrame to a JSON file

df.to_json('output.json', orient='records', indent=4)

Conclusion

Python’s standard libraries provide efficient tools for reading from and writing to .txt, .csv, and .json files. By using simple methods such as open(), csv.reader(), and json.load(), you can handle file operations effectively in your applications. These capabilities are especially useful in data analysis, configuration management, and integration with external systems.