... # nothing to split on - line too long
```
-So _Black_ will eventually format it like this:
+So _Black_ will, when we implement this, format it like this:
```py3
with \
... # backslashes and an ugly stranded colon
```
-Although when the target version is Python 3.9 or higher, _Black_ will use parentheses
-instead since they're allowed in Python 3.9 and higher.
+Although when the target version is Python 3.9 or higher, _Black_ uses parentheses
+instead in `--preview` mode (see below) since they're allowed in Python 3.9 and higher.
An alternative to consider if the backslashes in the above formatting are undesirable is
to use {external:py:obj}`contextlib.ExitStack` to combine context managers in the
Unnecessary parentheses are stripped. The stability and status of this feature is
tracked in [this issue](https://github.com/psf/black/issues/2188).
-### Improved empty line management
+### Improved line breaks
-1. _Black_ will remove newlines in the beginning of new code blocks, i.e. when the
- indentation level is increased. For example:
-
- ```python
- def my_func():
-
- print("The line above me will be deleted!")
- ```
-
- will be changed to:
-
- ```python
- def my_func():
- print("The line above me will be deleted!")
- ```
-
- This new feature will be applied to **all code blocks**: `def`, `class`, `if`,
- `for`, `while`, `with`, `case` and `match`.
-
-2. _Black_ will enforce empty lines before classes and functions with leading comments.
- For example:
-
- ```python
- some_var = 1
- # Leading sticky comment
- def my_func():
- ...
- ```
-
- will be changed to:
-
- ```python
- some_var = 1
-
-
- # Leading sticky comment
- def my_func():
- ...
- ```
-
-### Improved parentheses management
-
-_Black_ will format parentheses around return annotations similarly to other sets of
-parentheses. For example:
+For assignment expressions, _Black_ now prefers to split and wrap the right side of the
+assignment instead of left side. For example:
```python
-def foo() -> (int):
- ...
-
-def foo() -> looooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooong:
- ...
+some_dict[
+ "with_a_long_key"
+] = some_looooooooong_module.some_looooooooooooooong_function_name(
+ first_argument, second_argument, third_argument
+)
```
will be changed to:
```python
-def foo() -> int:
- ...
-
-
-def foo() -> (
- looooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooong
-):
- ...
+some_dict["with_a_long_key"] = (
+ some_looooooooong_module.some_looooooooooooooong_function_name(
+ first_argument, second_argument, third_argument
+ )
+)
```
-And, extra parentheses in `await` expressions and `with` statements are removed. For
-example:
+### Improved parentheses management
-```python
-with ((open("bla.txt")) as f, open("x")):
- ...
+For dict literals with long values, they are now wrapped in parentheses. Unnecessary
+parentheses are now removed. For example:
-async def main():
- await (asyncio.sleep(1))
+```python
+my_dict = {
+ my_dict = {
+ "a key in my dict": a_very_long_variable
+ * and_a_very_long_function_call()
+ / 100000.0,
+ "another key": (short_value),
+}
```
will be changed to:
```python
-with open("bla.txt") as f, open("x"):
- ...
-
-
-async def main():
- await asyncio.sleep(1)
+my_dict = {
+ "a key in my dict": (
+ a_very_long_variable * and_a_very_long_function_call() / 100000.0
+ ),
+ "another key": short_value,
+}
```