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gh-155087: Add ternary conditional operator (?:) and $-prefix None-declaration syntax#155089

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gh-155087: Add ternary conditional operator (?:) and $-prefix None-declaration syntax #155089

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b156e63
New features calle ternary and declaration
rajdeepdeyon2022-hub Aug 1, 2026
cae3525
New changes
rajdeepdeyon2022-hub Aug 1, 2026
594b91f
Add dollar-declaration () syntax and assignment-aware ternary (?:) op…
rajdeepdeyon2022-hub Aug 2, 2026
136490f
Finalize grammar and token changes
rajdeepdeyon2022-hub Aug 2, 2026
97998dd
Add dollar-declaration () syntax and assignment-aware ternary (?:) op…
rajdeepdeyon2022-hub Aug 2, 2026
4e3560f
Merge clean grammar changes into features
rajdeepdeyon2022-hub Aug 2, 2026
36151f5
Merge branch 'main' into features
RAJ0793 Aug 2, 2026
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212 changes: 108 additions & 104 deletions Doc/library/token-list.inc
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2 changes: 2 additions & 0 deletions Grammar/Tokens
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Original file line numberDiff line numberDiff line change
Expand Up@@ -59,6 +59,8 @@ RARROW '->'
ELLIPSIS '...'
COLONEQUAL ':='
EXCLAMATION '!'
DOLLAR '$'
TERNARY '?'

OP
TYPE_IGNORE
Expand Down
40 changes: 37 additions & 3 deletions Grammar/python.gram
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Expand Up@@ -119,6 +119,7 @@ simple_stmts[asdl_stmt_seq*]:
# NOTE: assignment MUST precede expression, else parsing a simple assignment
# will throw a SyntaxError.
simple_stmt[stmt_ty] (memo):
| dollar_stmt
| assignment
| &"type" type_alias
| &('import' | 'from' | "lazy") import_stmt
Expand All@@ -134,6 +135,20 @@ simple_stmt[stmt_ty] (memo):
| &'global' global_stmt
| &'nonlocal' nonlocal_stmt

dollar_stmt[stmt_ty]:
| '$' n=NAME {
_PyAST_Assign(
CHECK(asdl_expr_seq*,
_PyPegen_singleton_seq(
p,
_PyAST_Name(n->v.Name.id, Store, EXTRA)
)
),
_PyAST_Constant(Py_None, NULL, EXTRA),
NULL,
EXTRA
)
}
compound_stmt[stmt_ty]:
| &('def' | '@' | 'async') function_def
| &'if' if_stmt
Expand DownExpand Up@@ -717,13 +732,25 @@ expression[expr_ty] (memo):
| invalid_if_expression
| invalid_expression
| invalid_legacy_expression
| question_if_expression
| if_expression
| disjunction
| lambdef

# IMPORTANT:
# The 'no' branch must be 'expression' (which includes question_if_expression
# as one of its alternatives), NOT question_if_expression directly.
# question_if_expression only matches "X ? Y : Z" shape; using it directly
# for 'no' forces the false-branch to ALSO be a ternary, breaking simple
# cases like "12 > 2 ? 5 : 4" where 4 is just a plain expression.
question_if_expression[expr_ty]:
| cond=disjunction '?' yes=expression ':' no=expression {
_PyAST_IfExp(cond, yes, no, EXTRA)
Comment on lines +747 to +748

@chatgpt-codex-connectorchatgpt-codex-connectorBotAug 2, 2026

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P2 Badge Gate the new syntax by feature_version

When callers parse with an older grammar via PyCF_ONLY_AST/ast.parse(..., feature_version=(3, 15)), this rule still accepts a ? b : c because it constructs IfExp directly instead of using CHECK_VERSION. Since this tree is already Python 3.16 (PY_MINOR_VERSION is 16), the new ?: syntax (and the new $ statement rule) should be wrapped in a version check so tools that request an older grammar continue to reject it.

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}
if_expression[expr_ty]:
| a=disjunction 'if' b=disjunction 'else' c=expression { _PyAST_IfExp(b, a, c, EXTRA) }

| a=disjunction 'if' b=disjunction 'else' c=expression {
_PyAST_IfExp(b, a, c, EXTRA)
}
yield_expr[expr_ty]:
| 'yield' 'from' a=expression { _PyAST_YieldFrom(a, EXTRA) }
| 'yield' a=[star_expressions] { _PyAST_Yield(a, EXTRA) }
Expand DownExpand Up@@ -1239,11 +1266,17 @@ invalid_kwarg:
| a='**' expression '=' b=expression {
RAISE_SYNTAX_ERROR_KNOWN_RANGE(a, b, "cannot assign to keyword argument unpacking") }

# IMPORTANT: Note that the "_without_invalid" suffix causes the rule to not call invalid rules under it
# IMPORTANT:
# expression_without_invalid must ALSO recognize question_if_expression,
# otherwise the invalid_* rules (which run BEFORE question_if_expression
# in the main `expression` rule) will treat '?' as a syntax error before
# ever letting question_if_expression get a chance to parse it.
expression_without_invalid[expr_ty]:
| a=disjunction 'if' b=disjunction 'else' c=expression { _PyAST_IfExp(b, a, c, EXTRA) }
| question_if_expression
| disjunction
| lambdef

invalid_legacy_expression:
| a=NAME !'(' b=star_expressions {
_PyPegen_check_legacy_stmt(p, a) ? RAISE_SYNTAX_ERROR_KNOWN_RANGE(a, b,
Expand DownExpand Up@@ -1659,3 +1692,4 @@ invalid_bitwise_or:
? RAISE_SYNTAX_ERROR_KNOWN_RANGE(b, c, "invalid syntax. Maybe you meant 'or' or '|' instead of '||'?")
: NULL
}

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