解释 docs.python.org 语法

Question

我想学习如何正确使用return from the docs.python.org. But I was hindered by my ignorance on how to read their expression syntax. For example, expression，如何理解：

return_stmt ::=  "return" [expression_list]
expression_list    ::=  expression ("," expression)* [","]

Answer 1

一个return语句可以单独留下（方括号表示可选值）。

def foo():
  return

或者有一个要求的表达式，到很多（*表示zero-to-many），用逗号分隔

def bar()
  return True, (x for x in range(5) if x > 2), [1, 2, 3]

或者如果在所需表达式（或表达式列表）后有一个逗号，它 returns 一个元组

>>> def baz():
...   return True,
...
>>> baz()
(True,)

Interpreting docs.python.org syntax