File I/O and String Operations Flashcards

What does the `'b'` flag in `open('file', 'rb')` indicate?

Answer: Binary mode

The `'b'` flag opens the file in binary mode, reading/writing raw bytes instead of text.

Which method replaces occurrences of a substring in a string?

Answer: replace()

`str.replace(old, new)` returns a new string with all occurrences of `old` replaced by `new`.

What does `str.find('x')` return if 'x' is not in the string?

Answer: -1

`str.find()` returns `-1` when the substring is not found, unlike `index()` which raises `ValueError`.

Which string method counts non-overlapping occurrences of a substring?

Answer: count()

`str.count(sub)` returns the number of non-overlapping occurrences of the substring.

What does `os.path.join('folder', 'file.txt')` return on Linux?

Answer: folder/file.txt

`os.path.join()` combines path components using the OS-appropriate separator (`/` on Unix/Linux).

Which encoding is the default for text files opened with `open()` in Python 3?

Answer: UTF-8 on most systems (locale-dependent)

Python 3 uses the platform's default encoding (typically UTF-8) unless explicitly specified.