他实际想告诉你的是新的一行，不是让你写一个newline在那儿，比如一句代码太长了，直接回车会报错，你写个\再换行，就会当做同一行处理

一行写不下，用这个接着上边的，比如你写一个很长的字符串，一行写不完，因为python是以换行作为结束的，你要加这个才能表明你换行是因为写不下；

比如：
a = "wrewrewrwedewew
ewwwwewe"
这样写会报错；
a = "wereeweweweweweewew\
qrewqrwqrwqe"
这样就没问题了。

相当于同一行啊，哥。
只是说你一行下来，不太好看，所以切行排版，但不换行。
如果你是java程序员，看一下springmvc的策略文件DispatchServlet.properties的内容，也是这样子的
# Default implementation classes for DispatcherServlet's strategy interfaces.

Used as fallback when no matching beans are found in the DispatcherServlet context.

Not meant to be customized by application developers.

org.springframework.web.servlet.LocaleResolver=org.springframework.web.servlet.i18n.AcceptHeaderLocaleResolver

org.springframework.web.servlet.ThemeResolver=org.springframework.web.servlet.theme.FixedThemeResolver

org.springframework.web.servlet.HandlerMapping=org.springframework.web.servlet.handler.BeanNameUrlHandlerMapping,\
org.springframework.web.servlet.mvc.annotation.DefaultAnnotationHandlerMapping

org.springframework.web.servlet.HandlerAdapter=org.springframework.web.servlet.mvc.HttpRequestHandlerAdapter,\
org.springframework.web.servlet.mvc.SimpleControllerHandlerAdapter,\
org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter

org.springframework.web.servlet.HandlerExceptionResolver=org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerExceptionResolver,\
org.springframework.web.servlet.mvc.annotation.ResponseStatusExceptionResolver,\
org.springframework.web.servlet.mvc.support.DefaultHandlerExceptionResolver

org.springframework.web.servlet.RequestToViewNameTranslator=org.springframework.web.servlet.view.DefaultRequestToViewNameTranslator

org.springframework.web.servlet.ViewResolver=org.springframework.web.servlet.view.InternalResourceViewResolver

org.springframework.web.servlet.FlashMapManager=org.springframework.web.servlet.support.SessionFlashMapManager

直接看示例

url = "http://translate.google.cn/translate_a/single?client=t"\    
    "&sl=en&tl=zh-CN&hl=zh-CN&dt=at&dt=bd&dt=ex&dt=ld&dt=md&dt=qca"\    
    "&dt=rw&dt=rm&dt=ss&dt=t&ie=UTF-8&oe=UTF-8&clearbtn=1&otf=1&pc=1"\    
    "&srcrom=0&ssel=0&tsel=0&kc=2&tk=%s&q=%s"