How does Python handle repr for strings?

Question

I'm trying to emulate Python's repr exactly in Java; this includes the use of single quotes where possible. What method does Python use to determine what sort of quotes it should emit?

Edit: I'm looking for some actual code, somewhere in the web of Python. I've already looked at Objects/unicodeobject.c and some of Objects/strlib/, but I couldn't find anything besides escape sequences for Unicode.

Answer 1

I guess it will use single quotes unless it need to use it inside the string.

As show in:

print repr("Hello")
print repr('Hello')
print repr("Hell'o")
print repr('Hell"o')
print repr("""Hell'o Worl"o""")

Output:

'Hello'
'Hello'
"Hell'o" # only one using double quotes
'Hell"o'
'Hell\'o Worl"o' # handles the single quote with a \'

Answer 2

https://github.com/python/cpython/tree/master/Objects/unicodeobject.c

static PyObject *
unicode_repr(PyObject *unicode)
{ ...

unicode_repr in here github.com/python/cpython/blob/master/Objects/unicodeobject.c by the looks of it.

NOTE: I've updated this answer to remove out-of-date info and point to the current repo

Answer 3

From what I could extract out of Objects/byteobject.c (here), this is the section that does it:

quote = '\'';
if (smartquotes && squotes && !dquotes)
    quote = '"';
if (squotes && quote == '\'') {
    if (newsize > PY_SSIZE_T_MAX - squotes)
        goto overflow;
    newsize += squotes;
}

So, if there is no double quotes and there is single quotes it uses double quotes, otherwise single quotes.