Python with Statement

The Problem with Manual close()

When you call open() and close() manually, an exception raised between them means close() never runs, leaving the file open. You could wrap everything in try/finally, but Python gives you a cleaner built-in tool for this: the with statement.

f = open("data.txt", "r")
content = f.read()   # if this raises an error, close() below never runs
f.close()

What Is a Context Manager?

A context manager is any object that knows how to set itself up and clean itself up automatically, using special __enter__ and __exit__ methods. File objects returned by open() are context managers, so you can hand them to a with statement and Python guarantees close() is called when the block ends — success or failure.

with open("data.txt", "r") as f:
    content = f.read()
    print(content)

# file is automatically closed here, even if an error occurred above

Writing with a Context Manager

The same pattern works for writing and appending, keeping your code short and safe from forgotten close() calls.

with open("report.txt", "w") as f:
    f.write("Sales Report\n")
    f.write("Total: 4500\n")

Multiple Files at Once

You can open several files in a single with statement, separated by commas — handy for copying data from one file to another.

with open("source.txt", "r") as infile, open("copy.txt", "w") as outfile:
    for line in infile:
        outfile.write(line)

• with guarantees the file is closed, even if an exception is raised inside the block.
• No need to call close() yourself — this removes an entire class of bugs.
• It works with any context manager, not just files — locks, database connections, and more.
• This is considered the Pythonic, professional standard for file handling.