1# Grammar for Python
2
3# Note:  Changing the grammar specified in this file will most likely
4#        require corresponding changes in the parser module
5#        (../Modules/parsermodule.c).  If you can't make the changes to
6#        that module yourself, please co-ordinate the required changes
7#        with someone who can; ask around on python-dev for help.  Fred
8#        Drake <fdrake@acm.org> will probably be listening there.
9
10# NOTE WELL: You should also follow all the steps listed in PEP 306,
11# "How to Change Python's Grammar"
12
13# Commands for Kees Blom's railroad program
14#diagram:token NAME
15#diagram:token NUMBER
16#diagram:token STRING
17#diagram:token NEWLINE
18#diagram:token ENDMARKER
19#diagram:token INDENT
20#diagram:output\input python.bla
21#diagram:token DEDENT
22#diagram:output\textwidth 20.04cm\oddsidemargin  0.0cm\evensidemargin 0.0cm
23#diagram:rules
24
25# Start symbols for the grammar:
26#	file_input is a module or sequence of commands read from an input file;
27#	single_input is a single interactive statement;
28#	eval_input is the input for the eval() and input() functions.
29# NB: compound_stmt in single_input is followed by extra NEWLINE!
30file_input: (NEWLINE | stmt)* ENDMARKER
31single_input: NEWLINE | simple_stmt | compound_stmt NEWLINE
32eval_input: testlist NEWLINE* ENDMARKER
33
34decorator: '@' dotted_name [ '(' [arglist] ')' ] NEWLINE
35decorators: decorator+
36decorated: decorators (classdef | funcdef)
37funcdef: 'def' NAME parameters ['->' test] ':' suite
38parameters: '(' [typedargslist] ')'
39typedargslist: ((tfpdef ['=' test] ',')*
40                ('*' [tname] (',' tname ['=' test])* [',' '**' tname] | '**' tname)
41                | tfpdef ['=' test] (',' tfpdef ['=' test])* [','])
42tname: NAME [':' test]
43tfpdef: tname | '(' tfplist ')'
44tfplist: tfpdef (',' tfpdef)* [',']
45varargslist: ((vfpdef ['=' test] ',')*
46              ('*' [vname] (',' vname ['=' test])*  [',' '**' vname] | '**' vname)
47              | vfpdef ['=' test] (',' vfpdef ['=' test])* [','])
48vname: NAME
49vfpdef: vname | '(' vfplist ')'
50vfplist: vfpdef (',' vfpdef)* [',']
51
52stmt: simple_stmt | compound_stmt
53simple_stmt: small_stmt (';' small_stmt)* [';'] NEWLINE
54small_stmt: (expr_stmt | print_stmt  | del_stmt | pass_stmt | flow_stmt |
55             import_stmt | global_stmt | exec_stmt | assert_stmt)
56expr_stmt: testlist_star_expr (augassign (yield_expr|testlist) |
57                     ('=' (yield_expr|testlist_star_expr))*)
58testlist_star_expr: (test|star_expr) (',' (test|star_expr))* [',']
59augassign: ('+=' | '-=' | '*=' | '/=' | '%=' | '&=' | '|=' | '^=' |
60            '<<=' | '>>=' | '**=' | '//=')
61# For normal assignments, additional restrictions enforced by the interpreter
62print_stmt: 'print' ( [ test (',' test)* [','] ] |
63                      '>>' test [ (',' test)+ [','] ] )
64del_stmt: 'del' exprlist
65pass_stmt: 'pass'
66flow_stmt: break_stmt | continue_stmt | return_stmt | raise_stmt | yield_stmt
67break_stmt: 'break'
68continue_stmt: 'continue'
69return_stmt: 'return' [testlist]
70yield_stmt: yield_expr
71raise_stmt: 'raise' [test ['from' test | ',' test [',' test]]]
72import_stmt: import_name | import_from
73import_name: 'import' dotted_as_names
74import_from: ('from' ('.'* dotted_name | '.'+)
75              'import' ('*' | '(' import_as_names ')' | import_as_names))
76import_as_name: NAME ['as' NAME]
77dotted_as_name: dotted_name ['as' NAME]
78import_as_names: import_as_name (',' import_as_name)* [',']
79dotted_as_names: dotted_as_name (',' dotted_as_name)*
80dotted_name: NAME ('.' NAME)*
81global_stmt: ('global' | 'nonlocal') NAME (',' NAME)*
82exec_stmt: 'exec' expr ['in' test [',' test]]
83assert_stmt: 'assert' test [',' test]
84
85compound_stmt: if_stmt | while_stmt | for_stmt | try_stmt | with_stmt | funcdef | classdef | decorated
86if_stmt: 'if' test ':' suite ('elif' test ':' suite)* ['else' ':' suite]
87while_stmt: 'while' test ':' suite ['else' ':' suite]
88for_stmt: 'for' exprlist 'in' testlist ':' suite ['else' ':' suite]
89try_stmt: ('try' ':' suite
90           ((except_clause ':' suite)+
91	    ['else' ':' suite]
92	    ['finally' ':' suite] |
93	   'finally' ':' suite))
94with_stmt: 'with' with_item (',' with_item)*  ':' suite
95with_item: test ['as' expr]
96with_var: 'as' expr
97# NB compile.c makes sure that the default except clause is last
98except_clause: 'except' [test [(',' | 'as') test]]
99suite: simple_stmt | NEWLINE INDENT stmt+ DEDENT
100
101# Backward compatibility cruft to support:
102# [ x for x in lambda: True, lambda: False if x() ]
103# even while also allowing:
104# lambda x: 5 if x else 2
105# (But not a mix of the two)
106testlist_safe: old_test [(',' old_test)+ [',']]
107old_test: or_test | old_lambdef
108old_lambdef: 'lambda' [varargslist] ':' old_test
109
110test: or_test ['if' or_test 'else' test] | lambdef
111or_test: and_test ('or' and_test)*
112and_test: not_test ('and' not_test)*
113not_test: 'not' not_test | comparison
114comparison: expr (comp_op expr)*
115comp_op: '<'|'>'|'=='|'>='|'<='|'<>'|'!='|'in'|'not' 'in'|'is'|'is' 'not'
116star_expr: '*' expr
117expr: xor_expr ('|' xor_expr)*
118xor_expr: and_expr ('^' and_expr)*
119and_expr: shift_expr ('&' shift_expr)*
120shift_expr: arith_expr (('<<'|'>>') arith_expr)*
121arith_expr: term (('+'|'-') term)*
122term: factor (('*'|'/'|'%'|'//') factor)*
123factor: ('+'|'-'|'~') factor | power
124power: atom trailer* ['**' factor]
125atom: ('(' [yield_expr|testlist_gexp] ')' |
126       '[' [listmaker] ']' |
127       '{' [dictsetmaker] '}' |
128       '`' testlist1 '`' |
129       NAME | NUMBER | STRING+ | '.' '.' '.')
130listmaker: (test|star_expr) ( comp_for | (',' (test|star_expr))* [','] )
131testlist_gexp: (test|star_expr) ( comp_for | (',' (test|star_expr))* [','] )
132lambdef: 'lambda' [varargslist] ':' test
133trailer: '(' [arglist] ')' | '[' subscriptlist ']' | '.' NAME
134subscriptlist: subscript (',' subscript)* [',']
135subscript: test | [test] ':' [test] [sliceop]
136sliceop: ':' [test]
137exprlist: (expr|star_expr) (',' (expr|star_expr))* [',']
138testlist: test (',' test)* [',']
139dictsetmaker: ( (test ':' test (comp_for | (',' test ':' test)* [','])) |
140                (test (comp_for | (',' test)* [','])) )
141
142classdef: 'class' NAME ['(' [arglist] ')'] ':' suite
143
144arglist: (argument ',')* (argument [',']
145                         |'*' test (',' argument)* [',' '**' test]
146                         |'**' test)
147argument: test [comp_for] | test '=' test  # Really [keyword '='] test
148
149comp_iter: comp_for | comp_if
150comp_for: 'for' exprlist 'in' testlist_safe [comp_iter]
151comp_if: 'if' old_test [comp_iter]
152
153testlist1: test (',' test)*
154
155# not used in grammar, but may appear in "node" passed from Parser to Compiler
156encoding_decl: NAME
157
158yield_expr: 'yield' [testlist]
159