5. 表达式 Expressions

This chapter explains the meaning of the elements of expressions in Python.

本章描述了Python中表达式的组成元素的含义。

Syntax Notes: In this and the following chapters, extended BNFnotation will be used to describe syntax, not lexical analysis. When (one alternative of) a syntax rule has the form

句法注意：在本章和之后的章节中，描述句法时使用与词法分析时不同的扩展BNF记法。当某个句法规则（可能是可选的）具有如下形式

name ::= othername

and no semantics are given, the semantics of this form of name are the same as for othername.

并且未给出特定语义时，name的这种形式规则的意义就是其与othername含义相同。