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fix: Remove parenthesis around sole list items (psf#4312)
1 parent 17efac4 commit 96ca1b6

7 files changed

Lines changed: 436 additions & 3 deletions

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‎CHANGES.md‎

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@@ -17,6 +17,8 @@
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<!-- Changes that affect Black's preview style -->
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- Remove parentheses around sole list items (#4312)
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### Configuration
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<!-- Changes to how Black can be configured -->

‎docs/the_black_code_style/future_style.md‎

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@@ -38,6 +38,9 @@ Currently, the following features are included in the preview style:
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blocks when the line is too long
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- `pep646_typed_star_arg_type_var_tuple`: fix type annotation spacing between * and more
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complex type variable tuple (i.e. `def fn(*args: *tuple[*Ts, T]) -> None: pass`)
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- `remove_lone_list_item_parens`: remove redundant parentheses around lone list items
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(depends on unstable `hug_parens_with_braces_and_square_brackets` feature in some
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cases)
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(labels/unstable-features)=
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‎src/black/linegen.py‎

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@@ -507,6 +507,22 @@ def visit_NUMBER(self, leaf: Leaf) -> Iterator[Line]:
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normalize_numeric_literal(leaf)
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yield from self.visit_default(leaf)
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def visit_atom(self, node: Node) -> Iterator[Line]:
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"""Visit any atom"""
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if (
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Preview.remove_lone_list_item_parens in self.mode
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and len(node.children) == 3
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):
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first = node.children[0]
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last = node.children[-1]
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if (first.type == token.LSQB and last.type == token.RSQB) or (
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first.type == token.LBRACE and last.type == token.RBRACE
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):
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# Lists or sets of one item
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maybe_make_parens_invisible_in_atom(node.children[1], parent=node)
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yield from self.visit_default(node)
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def visit_fstring(self, node: Node) -> Iterator[Line]:
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# currently we don't want to format and split f-strings at all.
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string_leaf = fstring_to_string(node)
@@ -1643,9 +1659,6 @@ def maybe_make_parens_invisible_in_atom(
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not is_type_ignore_comment_string(middle.prefix.strip())
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):
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first.value = ""
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if first.prefix.strip():
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# Preserve comments before first paren
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middle.prefix = first.prefix + middle.prefix
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last.value = ""
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maybe_make_parens_invisible_in_atom(
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middle,
@@ -1657,6 +1670,13 @@ def maybe_make_parens_invisible_in_atom(
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# Strip the invisible parens from `middle` by replacing
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# it with the child in-between the invisible parens
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middle.replace(middle.children[1])
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if middle.children[0].prefix.strip():
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# Preserve comments before first paren
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middle.children[1].prefix = (
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middle.children[0].prefix + middle.children[1].prefix
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)
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if middle.children[-1].prefix.strip():
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# Preserve comments before last paren
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last.prefix = middle.children[-1].prefix + last.prefix

‎src/black/mode.py‎

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@@ -210,6 +210,9 @@ class Preview(Enum):
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docstring_check_for_newline = auto()
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remove_redundant_guard_parens = auto()
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parens_for_long_if_clauses_in_case_block = auto()
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# NOTE: remove_lone_list_item_parens requires
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# hug_parens_with_braces_and_square_brackets to remove parens in some cases
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remove_lone_list_item_parens = auto()
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pep646_typed_star_arg_type_var_tuple = auto()
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‎src/black/resources/black.schema.json‎

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@@ -91,6 +91,7 @@
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"docstring_check_for_newline",
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"remove_redundant_guard_parens",
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"parens_for_long_if_clauses_in_case_block",
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"remove_lone_list_item_parens",
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"pep646_typed_star_arg_type_var_tuple"
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]
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},

‎tests/data/cases/preview_remove_lone_list_item_parens.py‎

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@@ -0,0 +1,158 @@
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# flags: --preview
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items = [(123)]
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items = [(True)]
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items = [(((((True)))))]
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items = [(((((True,)))))]
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items = [((((()))))]
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items = [(x for x in [1])]
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items = {(123)}
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items = {(True)}
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items = {(((((True)))))}
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# Requires `hug_parens_with_braces_and_square_brackets` unstable style to remove parentheses
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# around multiline values
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items = [
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(
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{"key1": "val1", "key2": "val2", "key3": "val3"}
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if some_var == "long strings"
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else {"key": "val"}
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)
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]
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items = [
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(
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{"key1": "val1", "key2": "val2"}
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if some_var == ""
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else {"key": "val"}
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)
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]
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# Comments should not cause crashes
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items = [
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( # comment
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{"key1": "val1", "key2": "val2", "key3": "val3"}
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if some_var == "long strings"
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else {"key": "val"}
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)
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]
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items = [
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(
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{"key1": "val1", "key2": "val2", "key3": "val3"}
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if some_var == "long strings"
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else {"key": "val"}
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) # comment
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]
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items = [ # comment
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(
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{"key1": "val1", "key2": "val2", "key3": "val3"}
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if some_var == "long strings"
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else {"key": "val"}
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)
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]
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items = [
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(
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{"key1": "val1", "key2": "val2", "key3": "val3"}
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if some_var == "long strings"
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else {"key": "val"}
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)
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] # comment
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items = [
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(
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{"key1": "val1", "key2": "val2", "key3": "val3"} # comment
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if some_var == "long strings"
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else {"key": "val"}
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)
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]
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items = [ # comment
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( # comment
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{"key1": "val1", "key2": "val2", "key3": "val3"}
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if some_var == "long strings"
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else {"key": "val"}
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)
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]
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items = [
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(
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{"key1": "val1", "key2": "val2", "key3": "val3"}
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if some_var == "long strings"
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else {"key": "val"}
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) # comment
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] # comment
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# output
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items = [123]
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items = [True]
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items = [True]
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items = [(True,)]
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items = [()]
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items = [(x for x in [1])]
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items = {123}
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items = {True}
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items = {True}
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# Requires `hug_parens_with_braces_and_square_brackets` unstable style to remove parentheses
96+
# around multiline values
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items = [
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(
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{"key1": "val1", "key2": "val2", "key3": "val3"}
100+
if some_var == "long strings"
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else {"key": "val"}
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)
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]
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items = [{"key1": "val1", "key2": "val2"} if some_var == "" else {"key": "val"}]
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# Comments should not cause crashes
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items = [
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( # comment
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{"key1": "val1", "key2": "val2", "key3": "val3"}
110+
if some_var == "long strings"
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else {"key": "val"}
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)
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]
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items = [
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(
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{"key1": "val1", "key2": "val2", "key3": "val3"}
117+
if some_var == "long strings"
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else {"key": "val"}
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) # comment
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]
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items = [ # comment
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(
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{"key1": "val1", "key2": "val2", "key3": "val3"}
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if some_var == "long strings"
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else {"key": "val"}
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)
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]
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items = [
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(
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{"key1": "val1", "key2": "val2", "key3": "val3"}
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if some_var == "long strings"
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else {"key": "val"}
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)
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] # comment
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items = [
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(
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{"key1": "val1", "key2": "val2", "key3": "val3"} # comment
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if some_var == "long strings"
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else {"key": "val"}
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)
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]
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items = [ # comment
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( # comment
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{"key1": "val1", "key2": "val2", "key3": "val3"}
148+
if some_var == "long strings"
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else {"key": "val"}
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)
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]
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items = [
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(
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{"key1": "val1", "key2": "val2", "key3": "val3"}
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if some_var == "long strings"
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else {"key": "val"}
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) # comment
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] # comment

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