Python 如何控制PyYAML对数据使用的标量形式?
我有一个具有短字符串属性和长多行字符串属性的对象。我想将短字符串写为YAML引号标量,将多行字符串写为文字标量:Python 如何控制PyYAML对数据使用的标量形式?,python,yaml,pyyaml,Python,Yaml,Pyyaml,我有一个具有短字符串属性和长多行字符串属性的对象。我想将短字符串写为YAML引号标量,将多行字符串写为文字标量: my_obj.short = "Hello" my_obj.long = "Line1\nLine2\nLine3" 我希望YAML看起来像这样: short: "Hello" long: | Line1 Line2 Line3 我怎样才能指示Pyaml这样做?如果我调用yaml.dump(my_obj),它会产生类似dict的输出: {long: 'line1
my_obj.short = "Hello"
my_obj.long = "Line1\nLine2\nLine3"
我希望YAML看起来像这样:
short: "Hello"
long: |
Line1
Line2
Line3
我怎样才能指示Pyaml这样做?如果我调用yaml.dump(my_obj)
,它会产生类似dict的输出:
{long: 'line1
line2
line3
', short: Hello}
(不知道为什么长是双倍间隔的…)
我能告诉皮亚姆如何对待我的属性吗?我想影响订单和款式。基于
输出
我希望任何带有
\n
的输入都是块文字。使用yaml/representer.py
中的代码作为基础:
# -*- coding: utf-8 -*-
import yaml
def should_use_block(value):
for c in u"\u000a\u000d\u001c\u001d\u001e\u0085\u2028\u2029":
if c in value:
return True
return False
def my_represent_scalar(self, tag, value, style=None):
if style is None:
if should_use_block(value):
style='|'
else:
style = self.default_style
node = yaml.representer.ScalarNode(tag, value, style=style)
if self.alias_key is not None:
self.represented_objects[self.alias_key] = node
return node
a={'short': "Hello", 'multiline': """Line1
Line2
Line3
""", 'multiline-unicode': u"""Lêne1
Lêne2
Lêne3
"""}
print(yaml.dump(a))
print(yaml.dump(a, allow_unicode=True))
yaml.representer.BaseRepresenter.represent_scalar = my_represent_scalar
print(yaml.dump(a))
print(yaml.dump(a, allow_unicode=True))
输出
{multiline: 'Line1
Line2
Line3
', multiline-unicode: "L\xEAne1\nL\xEAne2\nL\xEAne3\n", short: Hello}
{multiline: 'Line1
Line2
Line3
', multiline-unicode: 'Lêne1
Lêne2
Lêne3
', short: Hello}
After override
multiline: |
Line1
Line2
Line3
multiline-unicode: "L\xEAne1\nL\xEAne2\nL\xEAne3\n"
short: Hello
multiline: |
Line1
Line2
Line3
multiline-unicode: |
Lêne1
Lêne2
Lêne3
short: Hello
爱上了,我得到了这个密码:
import yaml
def str_presenter(dumper, data):
if len(data.splitlines()) > 1: # check for multiline string
return dumper.represent_scalar('tag:yaml.org,2002:str', data, style='|')
return dumper.represent_scalar('tag:yaml.org,2002:str', data)
yaml.add_representer(str, str_presenter)
它使每个多行字符串都是块文字
我试图避免猴子修补的部分。
完全归功于@lbt和@J.F.Sebastian。您可以使用其RoundTripLoader/Dumper(免责声明:我是该软件包的作者)除了做您想做的事情之外,它还支持YAML 1.2规范(从2009年开始),并有一些其他改进:
import sys
from ruamel.yaml import YAML
yaml_str = """\
short: "Hello" # does keep the quotes, but need to tell the loader
long: |
Line1
Line2
Line3
folded: >
some like
explicit folding
of scalars
for readability
"""
yaml = YAML()
yaml.preserve_quotes = True
data = yaml.load(yaml_str)
yaml.dump(data, sys.stdout)
给出:
short: "Hello" # does keep the quotes, but need to tell the loader
long: |
Line1
Line2
Line3
folded: >
some like
explicit folding
of scalars
for readability
(包括注释,从前面的同一列开始)
您也可以从头开始创建此输出,但是
确实需要提供额外信息,例如折叠位置的明确位置。这是一种很好的方法,可以避免显式标记输入字符串。您可以使用
is_multiline=lambda s:len(s.splitlines())>1
自动识别Unicode换行符,并且对于一行不会返回true。@J.F.Sebastian很高兴看到这个漂亮的技巧。现在代码看起来好多了。非常感谢!嗯,风格=“|”
似乎没有影响pyyaml@jfs是的,但是pyyaml发射器将在两行上打印test\n
,并用单引号括起来,因此,如果此练习的目标是在字符串包含换行符时使用块样式而不是引号,那么我们必须像处理多行一样处理这种情况(无论这在技术上是否正确)。与其使用拆分行
,不如简单地测试数据中的'\n'是否更便宜,并做同样的事情。是否可以这样做,使其不会影响全局yaml状态,但会影响对转储()的单个调用
?@JasonS:这是一个很好的单独问题。您可以尝试使用重写的表示标量、表示dict方法将自己的转储程序类传递给yaml.dump
。由于某些原因,这在本例中不起作用:。有什么想法吗?这是一个很好的答案,非常适合我,谢谢!…但我想补充一点,这适用于yaml.dump()
但不适用于yaml.safe\u dump()
。除非有办法让它适用于我错过的yaml.safe\u dump()
。
import sys
from ruamel.yaml import YAML
yaml_str = """\
short: "Hello" # does keep the quotes, but need to tell the loader
long: |
Line1
Line2
Line3
folded: >
some like
explicit folding
of scalars
for readability
"""
yaml = YAML()
yaml.preserve_quotes = True
data = yaml.load(yaml_str)
yaml.dump(data, sys.stdout)
short: "Hello" # does keep the quotes, but need to tell the loader
long: |
Line1
Line2
Line3
folded: >
some like
explicit folding
of scalars
for readability