Python open(): Read and Write Files

The open() function opens a file for reading, writing, or appending. It’s useful for reading files, writing logs, processing large data, and managing file storage.

Example

file = open("example.txt", "r")  # Open file in read mode
content = file.read()  # Read file content
file.close()
print(content)

This opens, reads, and closes the file.

Syntax

open(file, mode="r", encoding=None)

• file → The name (or path) of the file to open.
• mode (optional) → Specifies read (r), write (w), append (a), etc.
• encoding (optional) → Commonly "utf-8" for text files.
• Returns → A file object.

1. Reading a File (r Mode)

with open("data.txt", "r") as file:
    print(file.read())  # Reads the entire file

The with statement automatically closes the file.

2. Writing to a File (w Mode)

with open("data.txt", "w") as file:
    file.write("Hello, World!")

Overwrites existing content.

3. Appending to a File (a Mode)

with open("data.txt", "a") as file:
    file.write("\nNew line added!")

Adds content without deleting previous data.

4. Reading a File Line by Line

with open("data.txt", "r") as file:
    for line in file:
        print(line.strip())  # Remove extra spaces

Efficient for large files.

5. Reading a File as a List

with open("data.txt", "r") as file:
    lines = file.readlines()
print(lines)

Stores each line as a list item.

6. Handling File Not Found Errors

try:
    with open("missing.txt", "r") as file:
        print(file.read())
except FileNotFoundError:
    print("File not found!")

Prevents program crashes when files are missing.

File Modes

Mode	Description
"r"	Read (default)
"w"	Write (creates/overwrites)
"a"	Append (adds to existing)
"x"	Create (fails if file exists)
"rb"	Read in binary mode
"wb"	Write in binary mode
"r+"	Read & write (keeps content)
"w+"	Read & write (overwrites)

Key Notes

• ✔ Reads, writes, and appends to files.
• ✔ with open() ensures files are closed properly.
• ✔ Use "utf-8" encoding for text files.
• ✔ Handle missing files with try-except.

By using open(), you can manage files efficiently, making it essential for file processing, logging, and data storage. 🚀