请教一个《Learn Python the Hard Way》上的问题。

[雪团老四]

原代码如下图所示：

输出如下图所示：

请问一下，为什么程序的最后一行输出中，既有单引号，又有双引号？是什么导致的呢？

[extend]

看第三句，里面有个单引号。 简单来说，看例子： 句子里面有单引号，要么用双号，要么转义，直接用单引号，错。 >>> print("let's go") let's go >>> print('let\'s go') let's go >>> print('let's go') SyntaxError: invalid syntax 句子里面有双引号，要么用单引号，要么转义，直接用双引号，错。 >>> print('let "go"') let "go" >>> print("let \"go\"") let "go" >>> print("let "go"") SyntaxError: invalid syntax 又有单引号，又有双引号怎么办。用单引双引无所谓，转义。 >>> print('let\'s "go"') let's "go" >>> print("let\'s \"go\"") let's "go" 所以你的第三句，里面有个单引号，输出结果一定是用双引号包围的。

[碧水幽幽泉]

第三行输出单引号和双引号，是因为didn't的原因。

>>> formatter = "%r %r %r %r"
>>> print (formatter % ("I had this thing.",
"That you could type up right.",
"But it didn't sing.",
"So I said goodnight."
))
'I had this thing.' 'That you could type up right.' "But it didn't sing." 'So I said goodnight.'

将didn't换成did not，就不会输出双引号了。

>>> print (formatter % ("I had this thing.",
"That you could type up right.",
"But it did not sing.",
"So I said goodnight."
))

'I had this thing.' 'That you could type up right.' 'But it did not sing.' 'So I said goodnight.'

[雪团老四]

谢谢，讲得很清楚全面，明白了。

引用 1 楼 extend 的回复:

看第三句，里面有个单引号。 简单来说，看例子： 句子里面有单引号，要么用双号，要么转义，直接用单引号，错。 >>> print("let's go") let's go >>> print('let\'s go') let's go >>> print('let's go') SyntaxError: invalid syntax 句子里面有双引号，要么用单引号，要么转义，直接用双引号，错。 >>> print('let "go"') let "go" >>> print("let \"go\"") let "go" >>> print("let "go"") SyntaxError: invalid syntax 又有单引号，又有双引号怎么办。用单引双引无所谓，转义。 >>> print('let\'s "go"') let's "go" >>> print("let\'s \"go\"") let's "go" 所以你的第三句，里面有个单引号，输出结果一定是用双引号包围的。

[雪团老四]

谢谢，明白了

引用 2 楼 qq646748739 的回复:

第三行输出单引号和双引号，是因为didn't的原因。

>>> formatter = "%r %r %r %r"
>>> print (formatter % ("I had this thing.",
"That you could type up right.",
"But it didn't sing.",
"So I said goodnight."
))
'I had this thing.' 'That you could type up right.' "But it didn't sing." 'So I said goodnight.'

将didn't换成did not，就不会输出双引号了。

>>> print (formatter % ("I had this thing.",
"That you could type up right.",
"But it did not sing.",
"So I said goodnight."
))

'I had this thing.' 'That you could type up right.' 'But it did not sing.' 'So I said goodnight.'