file.writelines() Write lines
Last updated: 2026-09-22
file.writelines() Write lines
file.writelines(lines) writes a sequence of strings; no newline is added automatically.
| Category | File Methods |
|---|---|
| Kind | Built-in Type Method |
| Python Version | all |
📝 Syntax
file.writelines()⚙️ Parameters
| lines Required | A sequence of strings (list, tuple, ...); no newlines are added automatically. |
|---|
Returns：None. Writes each string in lines to the file.
Mutates the original：No (returns a new object)
💥 Raises
TypeError— Raised when lines is not iterable or an element is not a string.OSError— Raised when the file is read-only, closed, or the write fails.
▶ Example
Edit the code, press Run, and see the result in the output panel:
Output：
a
b
💡 Related Cases
More case studies coming soon — check back later.
❓ FAQ
QDoes writelines() add newlines automatically?
ANo! It writes the strings in the sequence as-is. To write one per line you must add '\n' yourself, e.g. f.writelines(line + '\n' for line in lines).
QWhat is the difference from write()?
Awritelines() takes a sequence of strings and writes them one by one; write() takes a single string. Neither adds newlines automatically.
QWhat happens when an element is not a string?
AA TypeError is raised; you need to convert it to str first.
QWhat is the recommended way to write multiple lines?
Af.writelines(line + '\n' for line in lines), remembering to add the newline yourself.
