running to completion. The @gen.coroutine decorator communicates with the generator via the yield expressions, and with the coroutine’s caller by returning a Future. Here is a simplified version of the coroutine Tornado template is just HTML (or any other text-based format) with Python control sequences and expressions embedded within the markup:

Tornado templates support control statements and expressions. Control statements are surrounded by {% and %}, e.g. {% if len(items) > 2 %}. Expressions are surrounded by {{ and }}, e.g. {{ items[0] }}

running to completion. The @gen.coroutine decorator communicates with the generator via the yield expressions, and with the coroutine’s caller by returning a Future. Here is a simplified version of the coroutine Tornado template is just HTML (or any other text-based format) with Python control sequences and expressions embedded within the markup: Tornado templates support control statements and expressions. Control statements are surrounded by {% and %}, e.g. {% if len(items) > 2 %}. Expressions are surrounded by {{ and }}, e.g. {{ items[0] }}

重要区别。其他语言并没有这样的区别， 所以让我们看看语句与表达式有什么区别以及这些区别是如何影响函数体的。 • 语句（Statements）是执行一些操作但不返回值的指令。 • 表达式（Expressions）计算并产生一个值。 让我们看一些例子。 实际上，我们已经使用过语句和表达式。使用 let 关键字创建变量并绑定一个值是一个语句。 在示例 3-1 中，let y = 6; 是一个语句。 6); | ^^^ | = note: only supported directly in conditions of `if` and `while` expressions warning: unnecessary parentheses around assigned value --> src/main.rs:2:13 | 2 | let x