File operations in Python involve interacting with files on your computer’s storage system. These operations allow you to create, open, read, write, and manipulate files.
Core File Operations
Opening a File
The open() function is used to open a file. It returns a file object, which can be used to perform various operations on the file.
Python
file = open("filename.txt", "r")
The second argument specifies the mode in which the file is opened:
- “r”: Read mode (default)
- “w”: Write mode (creates a new file or overwrites an existing one)
- “a”: Append mode (adds to the end of an existing file)
- “x”: Create mode (creates a new file, raises an error if the file exists)
- “t”: Text mode (default)
- “b”: Binary mode
Reading from a File
read(): Reads the entire contents of the file as a string.readline(): Reads a single line from the file.readlines(): Reads all lines of the file and returns them as a list.
Code snippet
with open("data.txt", "r") as file:
content = file.read()
print(content)
Writing to a File
write(): Writes a string to the file.
Python
with open("output.txt", "w") as file:
file.write("This is some text.")
Closing a File
close(): Closes the file and releases system resources.- It’s generally recommended to use the
withstatement, which automatically closes the file.
- It’s generally recommended to use the
Python
with open("data.txt", "r") as file:
# Perform operations on the file
Other Common Operations
seek(offset, from_where): Moves the file pointer to a specific position within the file.tell(): Returns the current position of the file pointer.flush(): Writes the buffer to the disk.close(): Closes the file.
File Modes
- Text mode: Used for human-readable text files.
- Binary mode: Used for files containing raw data, like images or audio.
Error Handling
- Use
try-exceptblocks to handle potential errors likeFileNotFoundErrororPermissionError.
Additional Considerations
- Performance: For large files, consider using buffered I/O or memory-mapped files.
- File Paths: Use absolute or relative paths to specify file locations.
- File Formats: Different file formats have specific handling requirements.
By understanding these core operations and concepts, you can effectively work with files in your Python programs.
Why is file handling important?
It allows programs to store and retrieve data persistently, making data accessible even after the program terminates.
How do I open a file in Python?
Use the open() function with the desired file mode (e.g., “r”, “w”, “a”).
What happens if I don’t close a file?
The file might not be written to disk properly, and system resources might not be released.
What is the difference between open() and with open()?
with open() is preferred as it automatically closes the file when the block ends, even if an exception occurs.
How do I read a specific line from a file?
Use the readline() method or iterate over the file object.
How do I write to a file in append mode?
Open the file with the “a” mode and use the write() method.
How do I handle file not found errors?
Use a try-except block to catch FileNotFoundError.
How do I handle permission errors?
Use a try-except block to catch PermissionError.