inspect.signature does not respect PEP 8

[ilevkivskyi]

BPO	32018
Nosy	@gvanrossum, @ericvsmith, @bitdancer, @1st1, @ilevkivskyi, @corona10
PRs	bpo-32018: inspect.signature should follow PEP 8 #4408

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = <Date 2017-11-15.18:31:22.405>
created_at = <Date 2017-11-13.22:06:50.739>
labels = ['type-bug', '3.7']
title = 'inspect.signature does not respect PEP 8'
updated_at = <Date 2017-11-15.18:31:22.404>
user = 'https://github.com/ilevkivskyi'

bugs.python.org fields:

activity = <Date 2017-11-15.18:31:22.404>
actor = 'yselivanov'
assignee = 'none'
closed = True
closed_date = <Date 2017-11-15.18:31:22.405>
closer = 'yselivanov'
components = []
creation = <Date 2017-11-13.22:06:50.739>
creator = 'levkivskyi'
dependencies = []
files = []
hgrepos = []
issue_num = 32018
keywords = ['patch']
message_count = 6.0
messages = ['306171', '306172', '306174', '306175', '306295', '306296']
nosy_count = 6.0
nosy_names = ['gvanrossum', 'eric.smith', 'r.david.murray', 'yselivanov', 'levkivskyi', 'corona10']
pr_nums = ['4408']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue32018'
versions = ['Python 3.7']

[ilevkivskyi]

The string representation of a function signature with annotations is currently like this:

>>> def __init__(self, x: int = 1, y: int = 2) -> None: pass
... 
>>> import inspect
>>> str(inspect.signature(__init__))
'(self, x:str=1, y:int=2) -> None'

At the same time PEP-8 says:

When combining an argument annotation with a default value, use spaces around the = sign (but only for those arguments that have both an annotation and a default).

Yes:

def munge(sep: AnyStr = None): ...
def munge(input: AnyStr, sep: AnyStr = None, limit=1000): ...

No:

def munge(input: AnyStr=None): ...
def munge(input: AnyStr, limit = 1000): ...

I think there should be spaces in the signature repr.

[bitdancer]

FWIW, I find the version without the spaces to be more readable (but I don't find annotations to be readable in general, so my opinion may not be worth much :)

[gvanrossum]

Those people who read and write annotations regularly are all using the convention that was added to PEP-8, so let's make inspect follow that lead rather than argue about it here. :-)

[bitdancer]

Agreed.

[corona10]

I've submitted a patch. :)

[1st1]

New changeset 762b957 by Yury Selivanov (Dong-hee Na) in branch 'master':
bpo-32018: Fix inspect.signature repr to follow PEP-8 (bpo-4408)
762b957