Python File Operations Cheat Sheet
Quick reference for reading and writing files in Python. Master open modes, context managers, and reading line-by-line.
File Reading & Writing Methods
Primary methods used to read and write text or binary data from file streams.
| Method | Syntax | Description |
|---|---|---|
| read() | file.read(size=-1) | Reads and returns file contents up to size bytes. If size is negative or omitted, reads the entire file. |
| readline() | file.readline() | Reads a single line from the file. Returns an empty string at the End of File (EOF). |
| readlines() | file.readlines() | Reads all remaining lines from the file and returns them as a list of strings. |
| write() | file.write(string) | Writes the specified string to the file and returns the number of characters written. |
| writelines() | file.writelines(lines) | Writes a list of strings/lines to the file. Does not append newlines automatically. |
File Context and State Management
Managing resource opening, closing, navigation, and flushing.
| Method | Syntax | Description |
|---|---|---|
| open() | open(file, mode="r", encoding=None) | Opens a file path and returns a file object stream. |
| close() | file.close() | Closes the file stream. Necessary to release system resources if not using a context manager. |
| seek() | file.seek(offset, whence=0) | Moves the file cursor pointer to a specified byte position relative to whence. |
| tell() | file.tell() | Returns the current byte position of the file cursor. |
| flush() | file.flush() | Flushes the write buffers of the file stream to storage immediately. |
Frequently Asked Questions
Why is it recommended to use the with statement?
The with statement acts as a context manager, ensuring that the file is closed automatically when exiting the block, even if exceptions are raised.
What is the difference between r+ and w+ modes?
r+ opens a file for both reading and writing (without truncating the file). w+ opens it for reading and writing but truncates (erases) the file contents first.
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