1. 說明：
   1. 用三個雙引號來引用長字串．
   2. 在字串的行尾新增\
2. 注意：三個雙引號的字串會保留換行符，而反斜線不會保留，見示例
3. 例子：

#三個引號的示例

>>> print ("""
... This is a very long string.
... It continues here.
... END.
... """)

This is a very long string.
It continues here.
END.

#反斜線的示例
>>> print ("This is a long string \
... It continues here.\
 

... This is the end!")
This is a long string It continues here. This is the end