Reading and Writing Files in Python (The with open Guide)

Every useful program eventually needs to save data to a file or load data from one. When it comes to reading and writing files, Python makes this incredibly easy with the built-in open() function.

The “Old” (Unsafe) Way

You might see old tutorials do this when discussing reading and writing files in Python, but those may not provide the best practice, particularly with safety in mind.

f = open("my_file.txt", "w")
f.write("Hello!")
f.close()  # You MUST remember to close it!

If your program crashes before f.close() runs, the file might get corrupted or locked. This is a common mistake when learning about R and W files in Python, especially during file handling operations.

The “Modern” (Safe) Way: The with Statement

Python has a with statement (called a “context manager”) that automatically closes the file for you, even if errors happen. Always use this. Reading and writing files in Python using with is highly recommended for safe operations.

1. Writing to a File ("w" mode)

“w” stands for Write. Warning: This will overwrite any existing file with the same name, which may affect reading and writing operations in Python.

# This creates (or overwrites) 'example.txt'
with open("example.txt", "w") as file:
    file.write("Hello, world!\n")
    file.write("This is line 2.")

2. Appending to a File ("a" mode)

“a” stands for Append. This adds new data to the end of the file without deleting what’s already there, in addition to offering flexibility in Python.

with open("example.txt", "a") as file:
    file.write("\nThis is a new line added later.")

3. Reading from a File ("r" mode)

“r” stands for Read. This is the default mode if you don’t specify one, ensuring basic operations of reading files in Python.

try:
    with open("example.txt", "r") as file:
        content = file.read()
        print(content)
except FileNotFoundError:
    print("Error: The file does not exist yet.")

Pro Tip: Always wrap read operations in a try/except FileNotFoundError block to prevent crashes during reading and writing operations.

Summary Table