三重引号内可以有变量吗？如果可以，怎么做？

Question

这可能对一些人来说是个很简单的问题，但我搞不明白。你能在Python的三重引号中使用变量吗？

在下面这个例子中，怎么在文本中使用变量呢：

wash_clothes = 'tuesdays'
clean_dishes = 'never'

mystring =""" I like to wash clothes on %wash_clothes
I like to clean dishes %clean_dishes
"""

print(mystring)

我希望它的结果是：

 I like to wash clothes on tuesdays
     I like to clean dishes never

如果不能的话，处理那些需要几个变量的大段文本的最佳方法是什么呢？而且这些文本中还有很多特殊字符？

Answer 1

没错！从Python 3.6开始，你可以使用f字符串来实现这个功能：它们会直接在字符串中插入变量的值，所以在执行mystring = ...这一行后，mystring就会有你想要的值。

wash_clothes = 'tuesdays'
clean_dishes = 'never'

mystring = f"""I like to wash clothes on {wash_clothes}
I like to clean dishes {clean_dishes}
"""

print(mystring)

如果你需要在字符串中添加一个字面上的{或}，你只需要把它们写两遍：

if use_squiggly:
    kind = 'squiggly'
else:
    kind = 'curly'

print(f"""The {kind} brackets are:
  - '{{', or the left {kind} bracket
  - '}}', or the right {kind} bracket
""")

根据use_squiggly的值，这段代码会打印出以下内容：

The squiggly brackets are:
  - '{', or the left squiggly bracket
  - '}', or the right squiggly bracket

或者

The curly brackets are:
  - '{', or the left curly bracket
  - '}', or the right curly bracket

Answer 2

做这件事的推荐方式是使用 str.format()，而不是用 % 的方法：

这种字符串格式化的方法是Python 3.0中的新标准，应该在新代码中优先使用，而不是之前的 % 格式化方法。

举个例子：

wash_clothes = 'tuesdays'
clean_dishes = 'never'

mystring =""" I like to wash clothes on {0}
I like to clean dishes {1}
"""

print mystring.format(wash_clothes, clean_dishes)

Answer 3

在Python 2中，有一种方法：

>>> mystring =""" I like to wash clothes on %s
... I like to clean dishes %s
... """
>>> wash_clothes = 'tuesdays'
>>> clean_dishes = 'never'
>>> 
>>> print mystring % (wash_clothes, clean_dishes)
 I like to wash clothes on tuesdays
I like to clean dishes never

另外，可以看看字符串格式化的内容

• http://docs.python.org/library/string.html#string-formatting