python - 在双引号和单引号中打印

Question

我在 exercise 8 Learning Python the Hard Way，我不明白为什么 print 函数中的某些行用单引号或双引号打印。

程序如下:

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."
)

输出如下:

'I had this thing.' 'That you could type up right.' "But it didn't sing." 'So I said goodnight.'

为什么第三句是双引号，为什么其他的是单引号？

Answer 1

formatter 使用 %r 以便每个 str 都打印在引号中。执行此操作的函数默认使用单引号作为分隔符，但如果它在字符串中看到单引号而字符串中没有双引号，则会切换为使用双引号作为分隔符。

例如，尝试:

print "%r" % '''This string has a ' and a " in it.'''