Black wraps long Python expressions by looking for places to split in the expression’s bracket structure. It first tries to keep a complete expression or simple statement on one line; if that does not fit, it breaks inside matching brackets and, when needed, continues into nested brackets. The default line length is 88 characters, but it is a target rather than a hard maximum.
How Black decides where to wrap
Black formats according to syntax rather than by inserting a break at an arbitrary character count. Its style guide says it aims to render one full expression or simple statement per line. If the expression does not fit the configured line length, Black looks for a usable split inside its outer matching brackets. If the resulting line is still too long, it can split further inside nested bracket pairs.
For a comma-separated group inside brackets, Black first tries to keep the group together. If it cannot fit, it can expand the group so each item occupies its own line, with the closing bracket placed on its own line. This applies to calls and collections; the exact result depends on the expression’s structure and active Black style. See Black’s current style guide.
Illustrative example
This call has a natural split point at its parentheses and commas. The formatted layout below illustrates the kind of expansion Black uses when the arguments do not fit together; exact output can depend on the configured line length, Black version, and flags.
Free tools Windows power users keep installed
One-click scans. No signup required.
#1 Best Overall
- Read Before You Buy — No Video Output: These adapters support charging and USB 2.0 data transfer, but cannot transmit video signals. Except for standard USB webcams (which use USB data only), they are not compatible with HDMI/DisplayPort cables, video-capable USB-C hubs, or docking stations with video output.
- Convert USB-A Ports to USB-C: Designed to connect USB-C earphones, cables, flash drives, card readers, and other USB-C accessories to standard USB-A ports. Plug-and-play with no drivers or software required.
- Aluminum Alloy Housing: Built with a sturdy aluminum alloy shell that aids in heat dissipation and protects against daily wear and scratches. Designed to maintain a stable and secure connection.
- Compact & Travel-Friendly: The ultra-compact design allows the adapter to stay plugged into your device without blocking adjacent ports or adding bulk, reducing wear and tear on your original USB ports.
- 12-Month Warranty: Backed by a 12-month manufacturer warranty for peace of mind. Designed to meet strict quality control standards for reliable everyday performance.
render_report(customer_id, include_archived, output_format, destination_path)render_report(
customer_id,
include_archived,
output_format,
destination_path,
)The call’s outer parentheses provide the bracket pair, and commas separate the arguments. Nested calls, lists, dictionaries, and other bracketed expressions can provide additional places to split.
What the 88-character line length means
Black’s documented default is 88 characters per line. You can set a lower or higher line length, and Black tries to respect the selected value. It is not a strict cap: other formatting rules can prevent a compliant split, so an output line may exceed the configured length. The style guide also cautions against very long lines—particularly lines over 100 characters—because they can be harder to read and review.
Rank #2
- 5-in-1 USB-C Hub: Experience comprehensive connectivity featuring a Power Delivery input, two USB-A 2.0 ports, a USB-A 3.0 port, and an HDMI port. (Note: The USB-C power delivery input port is only for connecting an external wall charger to power your laptop and cannot power peripheral devices.)
- 90W Pass-Through Charging: Achieve optimal charging with 90W pass-through power to your laptop, supported by a total input of 100W, with the hub reserving 10W for operational efficiency. (Note: Wall charger not included.)
- Quick Data Transfers: Accelerate your productivity with rapid data transfers using a high-speed 5Gbps USB 3.0 port and two 480Mbps USB 2.0 ports.
- 4K HDMI Display: Enhance your visual experience with a hub capable of delivering 4K resolution at 30Hz in both mirror and extend modes. Please note that this hub is compatible with MacBook (macOS 12 and newer), Windows 10 and 11, ChromeOS, and laptops equipped with DP Alt Mode and Power Delivery. Note: This device is not compatible with Linux.
- What You Get: Anker USB-C Hub (5-in-1, 4K HDMI), welcome guide, 18-month warranty, and our friendly customer service.
When an expression stays long, check both the configured length and the available syntax-level split points. A long unbracketed expression may offer fewer useful breaks than a call or collection with commas. Black also formats multiline binary expressions with breaks before the operators, following its documented style.
Use a trailing comma to keep a group expanded
A trailing comma inside a bracketed, comma-separated group can signal that you want the expanded, one-item-per-line layout to remain. This is useful when a call or collection is short now but likely to gain items later. If you remove the trailing comma, Black may collapse the group onto one line when it fits.
Recommended Free Tools
Rank #3
- Sleek 7-in-1 USB-C Hub: Features an HDMI port, two USB-A 3.0 ports, and a USB-C data port, each providing 5Gbps transfer speeds. It also includes a USB-C PD input port for charging up to 100W and dual SD and TF card slots, all in a compact design.
- Flawless 4K@60Hz Video with HDMI: Delivers exceptional clarity and smoothness with its 4K@60Hz HDMI port, making it ideal for high-definition presentations and entertainment. (Note: Only the HDMI port supports video projection; the USB-C port is for data transfer only.)
- Double Up on Efficiency: The two USB-A 3.0 ports and a USB-C port support a fast 5Gbps data rate, significantly boosting your transfer speeds and improving productivity.
- Fast and Reliable 85W Charging: Offers high-capacity, speedy charging for laptops up to 85W, so you spend less time tethered to an outlet and more time being productive.
- What You Get: Anker USB-C Hub (7-in-1), welcome guide, 18-month warranty, and our friendly customer service.
To tell Black to ignore this signal, use --skip-magic-trailing-comma or its short form, -C. The behavior described here concerns bracketed comma-separated groups; do not assume every trailing comma in every syntax position produces the same layout. Option details are in Black’s usage documentation.
When brackets do not solve the line
Some expressions do not have comma-separated items that Black can expand. Parentheses can give a complex expression nested break points, but Black manages optional parentheses according to its style: it may remove them when the statement fits or when the inner expression has no further delimiters to split on, and add them in other cases. It does not freely add or remove arbitrary nested parentheses just to match a preferred visual grouping.
Rank #4
- Dual Converters, Infinite Potential：Includes 2× USB C male to USB A female adapters and 2× USB A male to USB C female adapters. Perfect for a wide range of uses—tablets with Bluetooth keyboards, expand USB ports on macbook, and more. Two different converters for all your daily needs
- Next-Level 10Gbps & 3A Charging: No more slow 480Mbps, this usb to usb c adapter has a transfer speed of up to 10Gbps, allowing you to do more transferring in less time. This usb adapter fits both USB A and USB C charger, supporting up to 3A fast charging
- Upgraded Exquisite Craftsmanship: With an aluminum alloy housing and metal connector, the usbc to usb adapter is extremely durable and sturdy. Rigorously tested to withstand more than 10,000 times of plugging and unplugging, ensuring long-lasting performance
- Broad Compatible: The usb c to usb adapter widely supports all USB C/ USB A devices like laptops, tablets, cellphones, car chargers, and phone chargers. Such as compatible with MacBook Pro/Air 2023/2022, Thunderbolt 4/3 Devices,Apple MagSafe Watch 9/8/7/SE/Ultra, iPad Pro 2022/2021, Samsung Galaxy S23/S20/S10, and iPhone 17/16/15 Pro. Plug and play
- Please Note: To reach 10Gbps speed, keep the cable under 3.3 ft. For USB A Male to USB C adapters, try flipping the USB C connector. USB C Male to USB A adapters support bidirectional 10Gbps transfer within 3.3 ft
For data structure literals and from imports that exceed the allotted line length, the documented style expands elements or imported names onto separate lines. Multiline binary expressions break before the operator. These conventions can make a line readable without guaranteeing that every individual line stays under the configured limit. The style guide’s sections on line length, trailing commas, and line breaks describe these rules.
Check the active style when output differs
Black’s stable style and its preview style are not interchangeable. The --preview flag opts into proposed formatting changes that may be disruptive and may vary across releases. Exact output can therefore depend on the installed Black version, project configuration, and whether preview is enabled. Check the version and flags used by your editor, command line, and CI before comparing results.
Outdated Drivers Are Slowing You Down
One free scan finds every outdated or missing driver and matches the right update for your exact hardware.Free scan · exact hardware matchPC Slower Than It Used to Be?
A free scan shows the junk files, broken settings and background clutter dragging Windows down - then fixes them in one click.Free scan · Windows 10 & 11Best Value
- 5-in-1 Connectivity: Equipped with a 4K HDMI port, a 5 Gbps USB-C data port, two 5 Gbps USB-A ports, and a USB C 100W PD-IN port. Note: The USB C 100W PD-IN port supports only charging and does not support data transfer devices such as headphones or speakers.
- Powerful Pass-Through Charging: Supports up to 85W pass-through charging so you can power up your laptop while you use the hub. Note: Pass-through charging requires a charger (not included). Note: To achieve full power for iPad, we recommend using a 45W wall charger.
- Transfer Files in Seconds: Move files to and from your laptop at speeds of up to 5 Gbps via the USB-C and USB-A data ports. Note: The USB C 5Gbps Data port does not support video output.
- HD Display: Connect to the HDMI port to stream or mirror content to an external monitor in resolutions of up to 4K@30Hz. Note: The USB-C ports do not support video output.
- What You Get: Anker 332 USB-C Hub (5-in-1), welcome guide, our worry-free 18-month warranty, and friendly customer service.
The official change log records stable style updates, including the 2025 stable style introduced in version 25.1.0; it does not make that version a claim about the newest release today. Consult the Black change log for release history, and the usage documentation for preview and configuration options.
Quick Recap
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
