Python的解析器是龙书里面所展示的LL(1)解析器。Grammar/Grammar模块包含了Python的Extended Backus-Naur Form (EBNF)语法规范。下面展示了该规范的一部分样式：

1 stmt: simple_stmt | compound_stmt

2 simple_stmt: small_stmt (‘;’ small_stmt)* [‘;’] NEWLINE

3 small_stmt: (expr_stmt | del_stmt | pass_stmt | flow_stmt |

4 import_stmt | global_stmt | nonlocal_stmt | assert_stmt)

5 expr_stmt: testlist_star_expr (augassign (yield_expr|testlist) |

6 (‘=’ (yield_expr|testlist_star_expr))*)

7 testlist_star_expr: (test|star_expr) (‘,’ (test|star_expr))* [‘,’]

8 augassign: (‘+=’ | ‘-=’ | ‘*=’ | ‘@=’ | ‘/=’ | ‘%=’ | ‘&=’ | ‘|=’ | ‘^=’

9 | ‘<<=’ | ‘>>=’ | ‘**=’ | ‘//=’)

10

11 del_stmt: ‘del’ exprlist

12 pass_stmt: ‘pass’

13 flow_stmt: break_stmt | continue_stmt | return_stmt | raise_stmt |

14 yield_stmt

15 break_stmt: ‘break’

16 continue_stmt: ‘continue’

17 return_stmt: ‘return’ [testlist]

18 yield_stmt: yield_expr

19 raise_stmt: ‘raise’ [test [‘from’ test]]

20 import_stmt: import_name | import_from

21 import_name: ‘import’ dotted_as_names

22 import_from: (‘from’ ((‘.’ | ‘…’)* dotted_name | (‘.’ | ‘…’)+)

23 ‘import’ (‘*’ | ‘(‘ import_as_names ‘)’ | import_as_names))

24 import_as_name: NAME [‘as’ NAME]

25 dotted_as_name: dotted_name [‘as’ NAME]

26 import_as_names: import_as_name (‘,’ import_as_name)* [‘,’]

27 dotted_as_names: dotted_as_name (‘,’ dotted_as_name)*

28 dotted_name: NAME (‘.’ NAME)*

29 global_stmt: ‘global’ NAME (‘,’ NAME)*

30 nonlocal_stmt: ‘nonlocal’ NAME (‘,’ NAME)*

31 assert_stmt: ‘assert’ test [‘,’ test]

32

33 …

当通过命令行将一个模块传递给Python解释器时，PyParser_ParseFileObject函数将被调用来初始化该模块的解析。该函数会将模块文件名作为参数来调用函数PyTokenizer_FromFile。这个函数会把模块内容分解成为合法的Python的token，或者在不合法的内容被检测到的时候抛出异常。