我有一个很长的疑问。我想用Python将它分成几行。在JavaScript中实现这一点的一种方法是使用几个句子并用+运算符将它们连接起来（我知道，也许这不是最有效的方法，但我并不真正关心这个阶段的性能，只是代码的可读性）。例子：
var long_string = 'some text not important. just garbage to' +
'illustrate my example';
我尝试在Python中做类似的事情，但没有成功，所以我使用了\来拆分长字符串。然而，我不确定这是否是唯一/最好/最蟒蛇的做法。看起来很尴尬。实际代码：
query = 'SELECT action.descr as "action", '\
'role.id as role_id,'\
'role.descr as role'\
'FROM '\
'public.role_action_def,'\
'public.role,'\
'public.record_def, '\
'public.action'\
'WHERE role.id = role_action_def.role_id AND'\
'record_def.id = role_action_def.def_id AND'\
'action.id = role_action_def.action_id AND'\
'role_action_def.account_id = ' + account_id + ' AND'\
'record_def.account_id=' + account_id + ' AND'\
'def_id=' + def_id
我使用递归函数来构建复杂的SQL查询。此技术通常可用于构建大型字符串，同时保持代码可读性。
# Utility function to recursively resolve SQL statements.
# CAUTION: Use this function carefully, Pass correct SQL parameters {},
# TODO: This should never happen but check for infinite loops
def resolveSQL(sql_seed, sqlparams):
sql = sql_seed % (sqlparams)
if sql == sql_seed:
return ' '.join([x.strip() for x in sql.split()])
else:
return resolveSQL(sql, sqlparams)
P.S.：看看很棒的python-sqlparse库，如果需要，可以打印SQL查询。
例如：
sql = ("select field1, field2, field3, field4 "
"from table "
"where condition1={} "
"and condition2={}").format(1, 2)
Output: 'select field1, field2, field3, field4 from table
where condition1=1 and condition2=2'
如果条件的值应该是字符串，可以这样做：
sql = ("select field1, field2, field3, field4 "
"from table "
"where condition1='{0}' "
"and condition2='{1}'").format('2016-10-12', '2017-10-12')
Output: "select field1, field2, field3, field4 from table where
condition1='2016-10-12' and condition2='2017-10-12'"
我发现，当构建长字符串时，您通常会做一些类似于构建SQL查询的事情，在这种情况下，这是最好的：
query = ' '.join(( # Note double parentheses. join() takes an iterable
"SELECT foo",
"FROM bar",
"WHERE baz",
))
Levon的建议很好，但可能容易出错：
query = (
"SELECT foo"
"FROM bar"
"WHERE baz"
)
query == "SELECT fooFROM barWHERE baz" # Probably not what you want
我个人认为，以下是用Python编写原始SQL查询的最佳（简单、安全和Python化）方法，尤其是在使用Python的sqlite3模块时：
query = '''
SELECT
action.descr as action,
role.id as role_id,
role.descr as role
FROM
public.role_action_def,
public.role,
public.record_def,
public.action
WHERE
role.id = role_action_def.role_id
AND record_def.id = role_action_def.def_id
AND action.id = role_action_def.action_id
AND role_action_def.account_id = ?
AND record_def.account_id = ?
AND def_id = ?
'''
vars = (account_id, account_id, def_id) # a tuple of query variables
cursor.execute(query, vars) # using Python's sqlite3 module
Pros
整洁而简单的代码（Pythonic！）避免SQL注入与Python 2和Python 3兼容（毕竟是Pythonic）不需要字符串串联无需确保每行最右边的字符是空格
Cons
由于查询中的变量被替换为？占位符，它可能会变得有点难以跟踪哪个？当查询中有很多Python变量时，将由哪个Python变量替换。
