在Python中格式化多行字典的正确方法是什么？

Question

在Python中，我想在代码中编写多行字典。有几种方法可以对其进行格式化。以下是我能想到的一些：

1. mydict = { "key1": 1,
              "key2": 2,
              "key3": 3, }
   

2. mydict = { "key1": 1,
              "key2": 2,
              "key3": 3,
            }
   

3. mydict = {
       "key1": 1,
       "key2": 2,
       "key3": 3,
   }
   

我知道上述任何一种在语法上都是正确的，但我假设 Python 字典有一种首选的缩进和换行样式。它是什么？

注意：这不是语法问题。以上所有内容（据我所知）都是有效的 Python 语句，并且彼此等效。

Answer 1

我用#3。对于长列表、元组等也是如此。它不需要在缩进之外添加任何额外的空格。一如既往，保持一致。

mydict = {
    "key1": 1,
    "key2": 2,
    "key3": 3,
}

mylist = [
    (1, 'hello'),
    (2, 'world'),
]

nested = {
    a: [
        (1, 'a'),
        (2, 'b'),
    ],
    b: [
        (3, 'c'),
        (4, 'd'),
    ],
}

同样，这是我在不引入任何空格的情况下包含大字符串的首选方法（就像使用三引号多行字符串时会得到的那样）：

data = (
    "iVBORw0KGgoAAAANSUhEUgAAABAAAAAQCAYAAAAf8/9hAAAABG"
    "l0RVh0U29mdHdhcmUAQWRvYmUgSW1hZ2VSZWFkeXHJZTwAAAEN"
    "xBRpFYmctaKCfwrBSCrRLuL3iEW6+EEUG8XvIVjYWNgJdhFjIX"
    "rz6pKtPB5e5rmq7tmxk+hqO34e1or0yXTGrj9sXGs1Ib73efh1"
    "AAAABJRU5ErkJggg=="
)

Answer 2

首先，就像Steven Rumbalski所说，“PEP8没有解决这个问题”，所以这是个人喜好的问题。

我会使用与您的格式 3 类似但不相同的格式。这是我的格式，以及原因。

my_dictionary = { # Don't think dict(...) notation has more readability
    "key1": 1, # Indent by one press of TAB (i.e. 4 spaces)
    "key2": 2, # Same indentation scale as above
    "key3": 3, # Keep this final comma, so that future addition won't show up as 2-lines change in code diff
    } # My favorite: SAME indentation AS ABOVE, to emphasize this bracket is still part of the above code block!
the_next_line_of_code() # Otherwise the previous line would look like the begin of this part of code

bad_example = {
               "foo": "bar", # Don't do this. Unnecessary indentation wastes screen space
               "hello": "world" # Don't do this. Omitting the comma is not good.
} # You see? This line visually "joins" the next line when in a glance
the_next_line_of_code()

btw_this_is_a_function_with_long_name_or_with_lots_of_parameters(
    foo='hello world',  # So I put one parameter per line
    bar=123,  # And yeah, this extra comma here is harmless too;
              # I bet not many people knew/tried this.
              # Oh did I just show you how to write
              # multiple-line inline comment here?
              # Basically, same indentation forms a natural paragraph.
    ) # Indentation here. Same idea as the long dict case.
the_next_line_of_code()

# By the way, now you see how I prefer inline comment to document the very line.
# I think this inline style is more compact.
# Otherwise you will need extra blank line to split the comment and its code from others.

some_normal_code()

# hi this function is blah blah
some_code_need_extra_explanation()

some_normal_code()

Answer 3

因为你的键是字符串，而且我们正在讨论可读性，所以我更喜欢：

mydict = dict(
    key1 = 1,
    key2 = 2,
    key3 = 3
)

Answer 4

flake8 – 一个用于在 python 代码中强制风格一致性的实用程序，它检查代码语法并提供改进它的说明 – 推荐这种格式（请参阅 https://www.flake8rules.com/rules/E133.html）：

mydict = {
    "key1": 1,
    "key2": 2,
    "key3": 3,
    }

Answer 5

通常，如果你有大的 python 对象，那么格式化它们是相当困难的。我个人更喜欢使用一些工具来实现这一点。

这里是 python-beautifier - www.cleancss.com/python-beautify 可以立即将您的数据转换为可定制的样式。

Answer 6

如果您配置了Black格式化程序，它将生成一行短词典：

{"some_key": some_value, "another_key": another_value}

当我想手动覆盖行长度配置并将字典格式设置为多行时，只需在字典中添加注释即可：

{
    # some descriptive comment
    "some_key": some_value, 
    "another_key": another_value
}

和Black将使字典保持多行。

Answer 7

根据我在教程和其他方面的经验，第二个似乎总是首选，但这是个人偏好的选择。

Answer 8

dict(rank = int(lst[0]),
                grade = str(lst[1]),
                channel=str(lst[2])),
                videos = float(lst[3].replace(",", " ")),
                subscribers = float(lst[4].replace(",", "")),
                views = float(lst[5].replace(",", "")))

Answer 9

通常，您不会在最后一个条目后包含逗号，但 Python 会为您纠正这一点。