强制repr()使用单引号

Question

我有个问题，有没有办法“强制”repr()在字符串周围创建单引号？

当我只使用repr()时会发生这种情况

print repr("test")
'test'
print repr("test'")
"test'"
print repr("test\"")
'test"'
print repr("test'\"")
'test\'"'

最后一个是我想要的，但我不想总是添加\\"来得到单引号。

编辑：，我不会将答案标记为已被接受，因为正如@martijn所指出的，我使用repr()的目的并不是为了它的目的。

Answer 1

如果您的对象总是一个字符串，您可以这样做：

def repr_single(s):
    return "'" + repr('"' + s)[2:]

print repr_single("test'")
'test\''

但是，正如所问的，我对这里的用例很好奇。

Answer 2

我曾经需要做类似的事情，但我希望它总是“更喜欢”使用双引号--意思是使用双引号，除非字符串中的双引号比单引号多(以尽量减少需要转义的单引号)。

我这样做的方法是对内置的str类进行子类化，并重写它的__repr__()方法。您可能会很容易地将它中的逻辑反转到相反的位置(以及强制使用的字符总是一个或另一个字符)。

FWIW，代码如下：

# -*- coding: iso-8859-1 -*-

# Special string subclass to override the default
# representation method. Main purpose is to
# prefer using double quotes and avoid hex
# representation on chars with an ord() > 128
class MsgStr(str):
    def __repr__(self):
        # use double quotes unless there are more of them in the string than
        # single quotes
        quotechar = '"' if self.count("'") >= self.count('"') else "'"
        rep = [quotechar]
        for ch in self:
            # control char?
            if ord(ch) < ord(' '):
                # remove the single quotes around the escaped representation
                rep += repr(str(ch)).strip("'")
            # does embedded quote match quotechar being used?
            elif ch == quotechar:
                rep += "\\"
                rep += ch
            # else just use others as they are
            else:
                rep += ch
        rep += quotechar

        return "".join(rep)

if __name__ == "__main__":
    s1 = '\tWürttemberg'
    s2 = MsgStr(s1)
    print "str    s1:", s1
    print "MsgStr s2:", s2
    print "--only the next two should differ--"
    print "repr(s1):", repr(s1), "# uses built-in string 'repr'"
    print "repr(s2):", repr(s2), "# uses custom MsgStr 'repr'"
    print "str(s1):", str(s1)
    print "str(s2):", str(s2)
    print "repr(str(s1)):", repr(str(s1))
    print "repr(str(s2)):", repr(str(s2))
    print "MsgStr(repr(MsgStr('\tWürttemberg'))):", MsgStr(repr(MsgStr('\tWürttemberg')))
    assert eval(MsgStr(repr(MsgStr('\tWürttemberg')))) == MsgStr('\tWürttemberg')

输出：

str    s1:  Württemberg
MsgStr s2:  Württemberg
--only the next two should differ--
repr(s1): '\tW\xfcrttemberg' # uses built-in string 'repr'
repr(s2): "\tWürttemberg" # uses custom MsgStr 'repr'
str(s1):    Württemberg
str(s2):    Württemberg
repr(str(s1)): '\tW\xfcrttemberg'
repr(str(s2)): '\tW\xfcrttemberg'
MsgStr(repr(MsgStr('    Württemberg'))): "\tWürttemberg"

Answer 3

我使用stdout的repr_double实现了repr_single

def repr_single(s):
    return "'" + repr('"' + s)[2:]

def repr_double(s):
    single = repr_single(s)
    return '"' + single[1:-1].replace('"', '\\"').replace('\\\'', '\'') + '"'

def test_single():
    assert r"'foobar'" == repr_single('foobar')
    assert r"'\'foobar'" == repr_single('\'foobar')
    assert "'\\'foobar'" == repr_single("'foobar")

def test_double():
    assert r'"foobar"' == repr_double("foobar")
    assert '"\'foobar"' == repr_double("'foobar")
    assert '"\\"foobar"' == repr_double('"foobar')