Triple-double quote v.s. Double quote

Question

What is the preferred way to write Python doc string?

""" or "

In the book Dive Into Python, the author provides the following example:

def buildConnectionString(params):
    """Build a connection string from a dictionary of parameters.

    Returns string."""

In another chapter, the author provides another example:

def stripnulls(data):
    "strip whitespace and nulls"
    return data.replace("\00", "").strip()

Both syntax work. The only difference to me is that """ allows us to write multi-line doc.

Is there any difference other than that?

Solution 1

From the PEP8 Style Guide:

• PEP 257 describes good docstring conventions. Note that most importantly, the """ that ends a multiline docstring should be on a line by itself, e.g.:

  """Return a foobang
  
  Optional plotz says to frobnicate the bizbaz first.
  """
  

• For one liner docstrings, it's okay to keep the closing """ on the same line.

PEP 257 recommends using triple quotes, even for one-line docstrings:

• Triple quotes are used even though the string fits on one line. This makes it easy to later expand it.

Note that not even the Python standard library itself follows these recommendations consistently. For example,

• abcoll.py
• ftplib.py
• functools.py
• inspect.py

Solution 2

They're both strings, so there is no difference. The preferred style is triple double quotes (PEP 257):

For consistency, always use """triple double quotes""" around docstrings.

Use r"""raw triple double quotes""" if you use any backslashes in your docstrings. For Unicode docstrings, use u"""Unicode triple-quoted strings""".