The writelines() method

The writelines() method is designed for writing multiple strings to a file in one go. Instead of calling write() repeatedly for each string, you pass an iterable object — like a list or a tuple — that contains the strings you want to write.

The method takes that iterable and writes each string from it into the file, one after another. It does not add any separators or newlines between the strings on its own. If you want each string to appear on a separate line, you must include the newline character \n at the end of each string yourself.

A key difference from the write() method: writelines() does not return the number of characters written. The write() method returns that count, but writelines() simply writes the content and returns nothing.

Here is the textbook's example to illustrate the usage:

>>> myobject = open("myfile.txt", 'w')
>>> lines = ["Hello everyone\n", "Writing #multiline strings\n", "This is the #third line"]
>>> myobject.writelines(lines)
>>> myobject.close()

When you open myfile.txt in Notepad, the content appears exactly as three separate lines, because each string in the list already contains a \n at its end.