Incorrect auto-indent in python code

Question

I have a following python code, which contains both 4 space and 2 space indents.

class Foo(object):
    def __init__(self,
                 flag = False):
      if flag:
        print("hello")
        print("how are you?")

When I auto-indent the python code below with gg=G, the above code becomes

class Model(object):
    def __init__(self,
                 flag = False):
        if flag:
            print("hello")
        print("how are you?")

The code is wrong because the last line should be under the if block. Why is this happening?

Answer 1

In this case, the auto-indentation seems confused because the def __init__() is indented by four spaces, while the others are indented by two spaces. This is valid Python, but the Vim Python indentation code doesn't seem to be advanced enough to deal with this.

In the Python source there's Tools/scripts/reindent.py, which can fix indentation. When I run it on your example it seems to work as expected.

You can use 'equalprg' to run this with =:

autocmd FileType python setlocal equalprg=/home/martin/src/Python-3.5.1/Tools/scripts/reindent.py

Some distros also package this script with the main Python package. Debian/Ubuntu puts it in the python-examples package.

There are also some other tools, like autopep8. Personally, I don't like autoformatting tools that do too much, as they break the most important style rule of all: think and do something sane.

I looked at the source of reindent.py, and it seems like a well-built script (Carpetsmoker seal of approval™). I believe autopep8 is used quite a lot, so I'll assume that works well enough too.