按原样将 SQL 保存到 YAML

我想以我自己的格式将 SQL 保存到 YAML 文件，如下所示：

(1)   
sql: SELECT DISTINCT p.id_product, 
                     p.price AS price, 
                     sp.reduction AS discount
       FROM ....

我使用 YAML 的以下设置

yaml.safe_dump(app_config,
               stream,
               indent=4,
               default_flow_style=False,
               encoding='utf-8',
               allow_unicode=True)

但是我得到了 YAML 的“经典”丑陋输出

(2)
sql: SELECT DISTINCT p.id_product, p.price AS price, sp.reduction AS discount, sp.reduction_type
    AS discount_type, pl.description_short AS description FROM ....

有什么办法可以实现输出#1吗？

附言。代表（配置）等于：

{'mapping': {'/*ID_LANG*/': 'AND pl.id_lang IN (/*VALUE*/)', '/*REFERENCE*/': "AND p.reference LIKE '%/*VALUE*/%'", }, 'sql': 'SELECT DISTINCT p.id_product, p.price AS price, sp.reduction AS discount, sp.reduction_type AS discount_type, pl.description_short AS description, pl.name AS name, i.id_image as image, p.reference AS model, m.name AS manufacturer, pl.available_now AS stock_status FROM /*PREFIX*/product p LEFT JOIN /*PREFIX*/product_lang pl ON (p.id_product = pl.id_product) LEFT JOIN /*PREFIX*/manufacturer m ON (m.id_manufacturer = p.id_manufacturer) LEFT JOIN /*PREFIX*/image i ON (i.id_product = p.id_product) LEFT JOIN /*PREFIX*/specific_price sp ON (sp.id_product = p.id_product) LEFT JOIN /*PREFIX*/category pc ON p.id_category_default = pc.id_category WHERE i.cover = 1 /*WHERE*/'}

如果您的输入格式是一些未格式化的 SQL（没有换行符和缩进空格），就像您似乎从输出 (2) 中获取的那样，您将never自动获得不错的输出：

import yaml

sql = ("SELECT DISTINCT p.id_product, "
                      "p.price AS price, "
                      "sp.reduction AS discount, "
                      "sp.reduction_type AS discount_type, "
                      "pl.description_short AS description "
                      "FROM ....")
app_config = dict(sql=sql)
print yaml.dump(app_config)

会给你：

{sql: 'SELECT DISTINCT p.id_product, p.price AS price, sp.reduction AS discount, sp.reduction_type
    AS discount_type, pl.description_short AS description FROM ....'}

正如你发现的那样。你可以尝试 使用换行符和缩进手动格式化字符串

app_config = dict(sql="""\
SELECT DISTINCT p.id_product,
                p.price AS price,
                sp.reduction AS discount,
                sp.reduction_type AS discount_type,
                pl.description_short AS description
    FROM ....""")
print yaml.dump(app_config)

但输出也好不到哪儿去：

{sql: "SELECT DISTINCT p.id_product,\n                p.price AS price,\n        \
    \        sp.reduction AS discount,\n                sp.reduction_type AS discount_type,\n\
    \                pl.description_short AS description\n    FROM ...."}

我建议你采取不同的方法并安装一个 sql 格式化程序，例如sqlparse https://pypi.python.org/pypi/sqlparse or 格式-sql https://pypi.python.org/pypi/format-sql结合鲁梅尔.yaml https://pypi.python.org/pypi/ruamel.yaml（我是 PyYAML 增强版的作者），它支持多行文字字符串往返。借助一点帮助，它还可以用于生成正确且外观更好（如果不是更好）的 YAML 输出。

你可以做：

import ruamel.yaml
from ruamel.yaml.scalarstring import PreservedScalarString
import sqlparse

sql = ("SELECT DISTINCT p.id_product, "
       "p.price AS price, "
       "sp.reduction AS discount, "
       "sp.reduction_type AS discount_type, "
       "pl.description_short AS description "
       "FROM ....")
fsql = sqlparse.format(sql, reindent=True, keyword_case="upper").encode('utf-8')

app_config = dict(sql=PreservedScalarString(fsql))
print ruamel.yaml.dump(app_config, Dumper=ruamel.yaml.RoundTripDumper)

并得到一个带有保留换行符的 YAML 文字标量 http://yaml.org/spec/1.2/spec.html#%7C%20literal%20style//:

sql: |-
  SELECT DISTINCT p.id_product,
                  p.price AS price,
                  sp.reduction AS discount,
                  sp.reduction_type AS discount_type,
                  pl.description_short AS description
  FROM ....

希望足够接近你想要的。