intermediate20 min
Working with Files
Reading from and writing to files in Python
Why Work with Files?
Reading and writing files lets your programs store data permanently — not just in memory while the program runs.
Note: In the browser (Pyodide), file operations work with a virtual filesystem. The concepts are the same as on a real computer!
Writing to a File
Writing Files
Output
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File Modes
"r"— Read (default)"w"— Write (overwrites existing file)"a"— Append (add to end)"r+"— Read and write
Reading Files
Reading Files
Output
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The with Statement
The with statement automatically closes the file when you're done — even if an error occurs. Always use with when working with files.
Appending to Files
Output
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Check Your Understanding
What file mode should you use to add content to an existing file without erasing it?
Check Your Understanding
Why is `with open(...) as f:` preferred over `f = open(...)`?
Exercise
Write a program that creates a file called `shopping.txt`, writes 3 items to it (one per line), then reads and prints the file contents.
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