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
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'"
该方法使用:
使用三引号字符串几乎没有内部标点符号使用检查模块去除局部压痕account_id和def_id变量使用Python 3.6格式的字符串插值('f')。
这种方式在我看来是最有蟒蛇风格的。
import inspect
query = inspect.cleandoc(f'''
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}'''
)
tl;dr:使用“”和“”来换行字符串,如中所示
string = """\
This is a long string
spanning multiple lines.
"""
从Python官方文档中:
字符串文本可以跨越多行。一种方法是使用三引号:“”“…”“”或“”“”…“”。行的结束是自动的包含在字符串中,但可以通过添加\在线路的末端。以下示例:
print("""\
Usage: thingy [OPTIONS]
-h Display this usage message
-H hostname Hostname to connect to
""")
生成以下输出(注意,初始换行符不是包括在内):
Usage: thingy [OPTIONS]
-h Display this usage message
-H hostname Hostname to connect to