Grammar/Grammar

# Grammar for Python, version 4

# Changes compared to version 3:
#	Removed 'dir' statement.
#	Function call argument is a testlist instead of exprlist.

# Changes compared to version 2:
#	The syntax of Boolean operations is changed to use more
#	conventional priorities: or < and < not.

# Changes compared to version 1:
#	modules and scripts are unified;
#	'quit' is gone (use ^D);
#	empty_stmt is gone, replaced by explicit NEWLINE where appropriate;
#	'import' and 'def' aren't special any more;
#	added 'from' NAME option on import clause, and '*' to import all;
#	added class definition.

# Start symbols for the grammar:
#	single_input is a single interactive statement;
#	file_input is a module or sequence of commands read from an input file;
#	expr_input is the input for the input() function;
#	eval_input is the input for the eval() function.

# NB: compound_stmt in single_input is followed by extra NEWLINE!
single_input: NEWLINE | simple_stmt | compound_stmt NEWLINE
file_input: (NEWLINE | stmt)* ENDMARKER
expr_input: testlist NEWLINE
eval_input: testlist ENDMARKER

funcdef: 'def' NAME parameters ':' suite
parameters: '(' [fplist] ')'
fplist: fpdef (',' fpdef)*
fpdef: NAME | '(' fplist ')'

stmt: simple_stmt | compound_stmt
simple_stmt: expr_stmt | print_stmt  | pass_stmt | del_stmt | flow_stmt | import_stmt
expr_stmt: (exprlist '=')* exprlist NEWLINE
# For assignments, additional restrictions enforced by the interpreter
print_stmt: 'print' (test ',')* [test] NEWLINE
del_stmt: 'del' exprlist NEWLINE
pass_stmt: 'pass' NEWLINE
flow_stmt: break_stmt | return_stmt | raise_stmt
break_stmt: 'break' NEWLINE
return_stmt: 'return' [testlist] NEWLINE
raise_stmt: 'raise' expr [',' expr] NEWLINE
import_stmt: 'import' NAME (',' NAME)* NEWLINE | 'from' NAME 'import' ('*' | NAME (',' NAME)*) NEWLINE
compound_stmt: if_stmt | while_stmt | for_stmt | try_stmt | funcdef | classdef
if_stmt: 'if' test ':' suite ('elif' test ':' suite)* ['else' ':' suite]
while_stmt: 'while' test ':' suite ['else' ':' suite]
for_stmt: 'for' exprlist 'in' exprlist ':' suite ['else' ':' suite]
try_stmt: 'try' ':' suite (except_clause ':' suite)* ['finally' ':' suite]
except_clause: 'except' [expr [',' expr]]
suite: simple_stmt | NEWLINE INDENT NEWLINE* (stmt NEWLINE*)+ DEDENT

test: and_test ('or' and_test)*
and_test: not_test ('and' not_test)*
not_test: 'not' not_test | comparison
comparison: expr (comp_op expr)*
comp_op: '<'|'>'|'='|'>' '='|'<' '='|'<' '>'|'in'|'not' 'in'|'is'|'is' 'not'
expr: term (('+'|'-') term)*
term: factor (('*'|'/'|'%') factor)*
factor: ('+'|'-') factor | atom trailer*
atom: '(' [testlist] ')' | '[' [testlist] ']' | '{' '}' | '`' testlist '`' | NAME | NUMBER | STRING
trailer: '(' [testlist] ')' | '[' subscript ']' | '.' NAME
subscript: expr | [expr] ':' [expr]
exprlist: expr (',' expr)* [',']
testlist: test (',' test)* [',']

classdef: 'class' NAME parameters ['=' baselist] ':' suite
baselist: atom arguments (',' atom arguments)*
arguments: '(' [testlist] ')'