从 Python 编写 yaml 的控制换行符

Question

我正在使用 Python 3 中的 yaml 库编写 YAML 文件，我想在编写长文本块时选择它放置换行符的位置。

这是我正在尝试做的事情的一个愚蠢的例子。 days 条目是一个很长的文本块，其中有几个项目用逗号分隔。我想将每个项目放在一条线上，但在此示例中，“9 Ladies Dancing”被拆分。

from yaml import safe_load, safe_dump

s = """\
- title: 12 Days of Christmas
- days: A partridge in a pear tree,
    2 Turtle Doves,
    3 French Hens,
    4 Calling Birds,
    5 Gold Rings,
    6 Geese a-Laying,
    7 Swans a-Swimming,
    8 Maids a-Milking,
    9 Ladies Dancing,
    10 Lords a-Leaping,
    11 Pipers Piping,
    12 Drummers Drumming
"""
l = safe_load(s)

print(safe_dump(l, default_flow_style=False))

打印出来：

- title: 12 Days of Christmas
- days: A partridge in a pear tree, 2 Turtle Doves, 3 French Hens, 4 Calling Birds,
    5 Gold Rings, 6 Geese a-Laying, 7 Swans a-Swimming, 8 Maids a-Milking, 9 Ladies
    Dancing, 10 Lords a-Leaping, 11 Pipers Piping, 12 Drummers Drumming

我想将days 的全文加载为一行，但我想将其打印为多行，最多 80 个字符，以便更容易检查项目的正确性。我想要一行中的多个项目，但我想以逗号分隔这些行，这样项目就不会跨行拆分。

Answer 1

一个简单的解决方案是将宽度设置为很大，但我不想这样做。

希望yaml 库有一个我还没有找到的功能，但这是我想出的最好的：

from yaml import safe_load, safe_dump, SafeDumper, dump

s = """\
- title: 12 Days of Christmas
- days: A partridge in a pear tree,
    2 Turtle Doves,
    3 French Hens,
    4 Calling Birds,
    5 Gold Rings,
    6 Geese a-Laying,
    7 Swans a-Swimming,
    8 Maids a-Milking,
    9 Ladies Dancing,
    10 Lords a-Leaping,
    11 Pipers Piping,
    12 Drummers Drumming
"""
l = safe_load(s)

print(safe_dump(l, default_flow_style=False))


class SplitDumper(SafeDumper):
    def write_plain(self, text, split=True):
        delimiter = ','
        if split:
            pieces = text.split(delimiter)
        else:
            pieces = [text]
        buffer = ''
        for i, piece in enumerate(pieces):
            if i > 0:
                buffer += delimiter
            if self.column-1 + len(buffer) + len(piece) <= self.best_width:
                buffer += piece
            else:
                super(SplitDumper, self).write_plain(buffer, split)
                self.write_indent()
                buffer = piece
        super(SplitDumper, self).write_plain(buffer)

print(dump(l, default_flow_style=False, Dumper=SplitDumper))

SplitDumper 类重写了write_plain() 方法，以逗号将其拆分为块，然后检测每行可以写入多少块。

打印出默认拆分，然后是自定义拆分：

- title: 12 Days of Christmas
- days: A partridge in a pear tree, 2 Turtle Doves, 3 French Hens, 4 Calling Birds,
    5 Gold Rings, 6 Geese a-Laying, 7 Swans a-Swimming, 8 Maids a-Milking, 9 Ladies
    Dancing, 10 Lords a-Leaping, 11 Pipers Piping, 12 Drummers Drumming

- title: 12 Days of Christmas
- days: A partridge in a pear tree, 2 Turtle Doves, 3 French Hens, 4 Calling Birds,
     5 Gold Rings, 6 Geese a-Laying, 7 Swans a-Swimming, 8 Maids a-Milking,
     9 Ladies Dancing, 10 Lords a-Leaping, 11 Pipers Piping, 12 Drummers Drumming

Answer 2

字符串加载后已经是单行了：

>>> l
[{'title': '12 Days of Christmas'}, {'days': 'A partridge in a pear tree, 2 Turtle Doves, 3 French Hens, 4 Calling Birds, 5 Gold Rings, 6 Geese a-Laying, 7 Swans a-Swimming, 8 Maids a-Milking, 9 Ladies Dancing, 10 Lords a-Leaping, 11 Pipers Piping, 12 Drummers Drumming'}]

您是否考虑过使用块？见Preserve new lines in YAML

>>> s = """\
... - title: 12 Days of Christmas
... - days: |-
...     A partridge in a pear tree,
...     2 Turtle Doves,
...     3 French Hens,
...     4 Calling Birds,
...     5 Gold Rings,
...     6 Geese a-Laying,
...     7 Swans a-Swimming,
...     8 Maids a-Milking,
...     9 Ladies Dancing,
...     10 Lords a-Leaping,
...     11 Pipers Piping,
...     12 Drummers Drumming
... """
>>> safe_load(s)
[{'title': '12 Days of Christmas'}, {'days': 'A partridge in a pear tree,\n2 Turtle Doves,\n3 French Hens,\n4 Calling Birds,\n5 Gold Rings,\n6 Geese a-Laying,\n7 Swans a-Swimming,\n8 Maids a-Milking,\n9 Ladies Dancing,\n10 Lords a-Leaping,\n11 Pipers Piping,\n12 Drummers Drumming'}]