21

I was just wondering what is the difference between two ways of writing Python Docstrings (__doc__):

  1. three single quotes:

    '''
Comment goes here
'''

  2. three double quotes:

    """
Comment goes here
"""

Is there any subtle difference in the way doc string could be formatted later while generating docs?

ivanleoncz
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prashu
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    Note: A "doc string" is just a *normal* string literal as far as the Python syntax/parser cares. The same rules for `"""`, `'''`, `"`, and `'` apply. –  Oct 26 '12 at 05:34

3 Answers3

18

No. They are the same. The only difference is that the first one can contain a sequence of three unescaped double quotes, while the second can contain a sequence of three unescaped single quotes. (In other words, because the delimiters are different, there is a slight difference in what characters you can use inside them.)

Docstrings are just regular strings, and in Python there is no difference between the different string delimiters, except that, of course, you can't use the string delimiter inside the string.

BrenBarn
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  • You said: "you can't use the string delimiter inside the string", but I tested it in python3: `foo = """abc"def"""` which succeeds, and foo has the value: `'abc"def'`. Also interestingly: `foo = """abc"'def"""` is also legal, producing: `'abc"\'def'`. – Eric Leschinski Jan 13 '16 at 22:14
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    @EricLeschinski: In that case, your string delimiter is `"""` (i.e., three double quotes), not `"`. – BrenBarn Jan 14 '16 at 04:07
14

The informational document PEP 257 -- Docstring Conventions recommends to use """triple double-quotes""" for consistency, and all their examples show the same:

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""".

Whether to use single quotes or double quotes is only a stylistic issue in practice. There will be no difference in formatting when generating and publishing docs from these strings.

wim
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8

Choose whatever style you want. Personally I use single quotes everywhere I can in Python.

The documentation states: 

"String literals can be enclosed in matching single quotes (') or double quotes (")."

It doesn't matter which one you decide to use. What does matter, is that you stick with your decision. It is good practice to choose a style and stick with it.

Aesthete
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  • Thanks @Aesthete. But, I am specially interested in understanding this for doc_strings (__doc__) for functions and classes. – prashu Oct 26 '12 at 05:26
  • @prashu A doc-strring is just .. a string. It's just *convention* (perhaps stated in a PEP somewhere?) to use the `"""` or `'''` quotes, generally to make life easier or more consistent or carry on a tradition .. and it is conceivable that some poorly written code inspection tools require it (but those are broken tools). However, the exact same string literal rules apply - try it! –  Oct 26 '12 at 05:32
  • A string is a string is a string is a string in Python. – Aesthete Oct 26 '12 at 05:38