Q.Does the seek() function work in the same manner for text and binary files?

No, the seek() function does not work in the same manner for text and binary files. The fundamental difference lies in how file positions (offsets) are interpreted and managed.

For binary files, seek() operates directly on byte offsets. You can move the file pointer to any arbitrary byte position within the file with precision. The offset value passed to seek() directly corresponds to the number of bytes from the reference point (beginning, current position, or end of file). This is straightforward because binary files are treated as raw sequences of bytes, without any character encoding or newline translation.

For text files, seek() is more restricted and less predictable. When a text file is opened, the operating system and the programming language's I/O library often perform character encoding and newline translation. For example, a single newline character \n in Python might be translated to \r\n (two bytes) on Windows when written to the file, and vice-versa when read. This means that an "offset" in terms of characters or lines does not necessarily correspond directly to a fixed byte offset.

The seek() function is used to change the current position of the file pointer within a file. This pointer determines where the next read or write operation will occur. While the fundamental purpose is the same, its behavior and permissible arguments differ significantly between text and binary files in Python.

seek() for Binary Files

When working with binary files (opened in modes like 'rb', 'wb', 'ab', 'rb+', etc.), seek() operates on byte offsets. This means you can move the file pointer to any specific byte position within the file.

The syntax for seek() in binary mode is typically file_object.seek(offset, whence).

• offset: An integer representing the number of bytes to move.
• whence: An optional integer argument that specifies the reference point for the offset.
  • 0 (or os.SEEK_SET): The offset is relative to the beginning of the file. This is the default value.
  • 1 (or os.SEEK_CUR): The offset is relative to the current file pointer position.
  • 2 (or os.SEEK_END): The offset is relative to the end of the file. In this case, the offset should typically be negative to move backward from the end.

For example, f.seek(100, 0) moves the pointer 100 bytes from the beginning. f.seek(-50, 2) moves the pointer 50 bytes backward from the end of the file.

seek() for Text Files

When working with text files (opened in modes like 'r', 'w', 'a', 'r+', etc.), seek() behaves differently and has significant restrictions. This is because text files involve character encoding (e.g., UTF-8, UTF-16). A single character might be represented by one, two, or more bytes, and this can vary. If you were to seek() to an arbitrary byte offset, you might land in the middle of a multi-byte character, leading to decoding errors or corrupted data.

To avoid these issues, seek() in text mode is restricted:

• The whence argument must be 0 (relative to the beginning of the file). You cannot use 1 (current position) or 2 (end of file).
• The offset argument must be either 0 (to go to the very beginning of the file) or a value previously returned by the tell() function. The tell() function in text mode returns an opaque "cookie" that represents a valid position within the file, which seek() can then safely use. …