Inconsistent spacing around top level functions

[zmwangx]

Operating system: macOS 10.14.2
Python version: 3.7.1
Black version: 18.9b0
Does also happen on master: yes

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I have a bit of OS-specific code that looks like this (when formatted by black):

import os

if os.name == "posix":
    import termios

    def foo():
        pass


elif os.name == "nt":
    try:
        import msvcrt

        def foo():
            pass

    except ImportError:

        def foo():
            pass


else:

    def foo():
        pass


other_code()

Note now foo has two empty lines below it most of the time (including in if..elif..else), except in the try block of a try..except.

Is this intentional? Seems to me there's no need to waste an extra line when the function definition is in any block; one empty line should be enough.

[ambv]

This is indeed the case: https://black.now.sh/?version=stable&state=_Td6WFoAAATm1rRGAgAhARYAAAB0L-Wj4AFlAKtdAD2IimZxl1N_WlwxRhR7MSgE-ANVlfGy-Pf-urovcUul06DGIKtNJ_PI3I6sH4UsuvCCJK3cSn3O4qbqqEoVdC4RVidtOakKqE1C2PRTK-dEU4CIhv140rXetsz6FlHHNcogH0t3yNeHxqr6iAwuCmSu430fNaT3oxW598BtIbDYmvw9WdVHpVPmNBsa5a2N64u1JlxqaEp3vqccXdLeWyZdVl1aJp0nIQ-QAAAA7ohML_SstGsAAccB5gIAAOsZSAKxxGf7AgAAAAAEWVo=

This is caused by Black discovering that those functions are in fact top level and applying two blank lines before the next top-level statement (which is why it doesn't happen before the except ImportError line in the example).

We'd accept a fix for this but probably not something we'll be working on soon.

[bukzor]

Is the only desired change to delete one blank line from each of those two double-blanks? Is that then the minimum amount of blank lines Black would allow?

[felix-hilden]

In my opinion a good style would be:

• No blanks after indenting in or out
• Exactly one blank line before and after defs and classes on the same level as other code

so the example provided would look like:

import os

if os.name == "posix":
    import termios

    def foo():
        pass
elif os.name == "nt":
    try:
        import msvcrt

        def foo():
            pass
    except ImportError:
        def foo():
            pass
else:
    def foo():
        pass

other_code()

I'm not 100 % sure about dropping the empty line after, I think leaving it up to the user would be okay. But this is fine in my opinion.

---

The linked PR addresses this to some extent, I think leaving the style at that would be okay too.