Strange formatting of fluent interface

Operating system: Mac
Python version: 3.7
Black version: 18.9b0
Does also happen on master:

Following on https://twitter.com/llanga/status/1052631100290420736

I have a code which uses yarl.URL

a = str(
    my_very_very_very_long_url_name
    .with_user(and_very_long_username)
    .with_password(and_very_long_password)
)

Black formats it like this

a = str(
    my_very_very_very_long_url_name.with_user(and_very_long_username).with_password(
        and_very_long_password
    )
)

I understand that first call is not on a new line because of reasons, but the rest still looks quite odd, especially considering that when there are three calls in the chain, Black produces

a = str(
    my_very_very_very_long_url_name.with_user(and_very_long_username)
    .with_user(and_very_long_username)
    .with_password(and_very_long_password)
)

Forgive me for using this as the fluent questions thread, but another case:

With a single call

def x():
    base_ds["security_score_filtered"] = base_ds["security_score_risk_adj"].where(
        base_ds["is_share_price_valid"]
        & base_ds["is_market_cap_valid"]
        & base_ds["is_liquid"]
    )

With two calls

def x():
    base_ds["security_score_filtered"] = (
        base_ds["security_score_risk_adj"]
        .where(
            base_ds["is_share_price_valid"]
            & base_ds["is_market_cap_valid"]
            & base_ds["is_liquid"]
        )
        .sum()  # <- new line here (only change)
    )

Why the switch of the first line between the two?

I would generally prefer the second format even without the second call (though the question stands independent of my opinion)

Adding another here, as a (hopefully) helpful additional case:

From:

    df = (
        gbq
        .read_gbq(query, project="sixty-capital-prod")
        .sort_values("factset_entity_id")
    )

To:

    df = gbq.read_gbq(query, project="sixty-capital-prod").sort_values(
        "factset_entity_id"
    )

And another:

Looks good:

                completion_time = (
                    a.read_namespaced_job(job.metadata.name, namespace="default")
                    .status()
                    .completion_time()
                )

Now without the () on the last two lines after status & completion_time :

                completion_time = a.read_namespaced_job(
                    job.metadata.name, namespace="default"
                ).status.completion_time

I would prefer that black applies the fluent style across more cases of chained calls and attribute accesses, such as those examples provided above, even if it does use a few more lines. Consistency between these similar multi-line expressions is more valuable to me than removing a few extra lines.

Is this possible to define flhent interface in black settings?

Related to my comment: #2279 (comment)

Since there are no maintainer comments yet on this issue, I'll echo the points already raised: I'd also like for Black to format fluent interfaces with or without initial parens consistently:

def func():
    (
        thing("argument-1")
        .thing("argument-2")
        .thing("argument-3")
        .thing("argument-4")
        .thing("argument-5")
        .thing("argument-6")
        .thing("argument-7")
        .thing("argument-8")
        .thing("argument-9")
    )

adding the parens rather than splitting a single call if the line is too long.

Here's a more complete set of variations I'd expect to behave similarly: playground

Regardless of the presence of initial surrounding parentheses, if the line is too long and there is a call chain we should add parens and split on method/attribute access (dots)
Whether or not the expression is an assignment should have no effect on the call chain formatting
Whether or not the calls contain any arguments should also not have an effect on the formatting beyond splitting further if the call itself is too long, unless:
Having magic trailing commas should explode the calls as normal

In the example playground, I find that the cases with no assignment and no initial parens are formatted against my expectations.

From #571 (comment) I suggest we add to the list:

Whether or not a member access is a call should have no effect on the call chain formatting

And in that case, #510 is very relevant, if not duplicate. But I'll leave it open for now.

Anything here?

@max-sixty

It would indeed be much appreciated if the formatting of fluent interfaces were more consistent. The examples posted by @max-sixty above are very descriptive of the issue.

With method chaining is often better for readability to have more lines but every method in the chain being called in a new line

anything here? this is currently the only thing that is holding me back from using black

Please write a PR to fix this issue instead of sending unproductive comments.

@vmgustavo

@vmgustavo I'm using # fmt : skip after the closing parenthesis of my fluent chains to keep my formatting when black breaks it.

@JelleZijlstra

@JelleZijlstra is it possible to provide custom method chains? So, this issue gets avoided, or is skipping format the only option here?

can we disable this with a flag?

Any comments from a maintainer? This feature would benefit the scientific Python community greatly since pandas encourages method chaining so much.

@JelleZijlstra

I'm using a lot of PySpark, and the following

retail_accounts_with_segment_df = (
    retail_accounts_df
    .withColumn("kim_segment_cd", f.lit("not applicable"))
    .withColumn("sbi_id", f.lit("not applicable"))
)

annoyingly gets formatted by black as:

retail_accounts_with_segment_df = retail_accounts_df.withColumn(
    "kim_segment_cd", f.lit("not applicable")
).withColumn("sbi_id", f.lit("not applicable"))

which is way less readable. I know you're looking for PR's, @JelleZijlstra , but not everyone is in the open source community business. Comments like this are just the users of these open source packages hoping to influence the prioritisation a little bit.

not everyone is in the open source community business. Comments like this are just the users of these open source packages hoping to influence the prioritisation a little bit.

There is no "business" and there is no "prioritisation". There are only PRs. Everyone here is a volunteer.

I'm locking this issue to prevent more unproductive notifications for the many people interested in this issue. PRs are still welcome!

Navigation Menu

Repository navigation

Strange formatting of fluent interface #571

With a single call

With two calls

Metadata

Assignees

Labels

Projects

Milestone

Relationships

Development

Strange formatting of fluent interface #571

Description

Activity

max-sixty commented on Mar 1, 2019

With a single call

With two calls

max-sixty commented on Mar 21, 2019

max-sixty commented on May 30, 2019

MrkGrgsn commented on Mar 10, 2020

vedal commented on Feb 11, 2021

peterHoburg commented on Oct 20, 2021

felix-hilden commented on Jan 31, 2022

felix-hilden commented on Jan 31, 2022

PeterJCLaw commented on Jan 31, 2022

felix-hilden commented on Jan 31, 2022

joshdunnlime commented on Mar 18, 2023

joaomacalos commented on May 1, 2023

vmgustavo commented on Jul 31, 2023

JelleZijlstra commented on Jul 31, 2023

joaomacalos commented on Aug 2, 2023

ion-elgreco commented on Aug 10, 2023

mo2menelzeiny commented on Mar 26, 2024

leotrs commented on Nov 24, 2024

tijlk commented on Nov 25, 2024

hauntsaninja commented on Nov 26, 2024

Metadata

Metadata

Assignees

Labels

Projects

Milestone

Relationships

Development

Issue actions