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

当前回答

嗯。

我知道这个问题发布已经很久了。但我刚刚找到了我想用来为项目中的变量分配长字符串和多行字符串的样式。这需要一点额外的运行时间,但仍然保留了代码的美感,即使我将字符串分配给的变量缩进很大。

    # Suppose the following code is heavily indented
    line3header = "Third"

    variable = fr"""

First line.
Second line.
{line3header} line.
{{}} line.
...
The last line.

    """.strip()
    """A variable whose name is Variable.

    You can even add a docstring here.
    """

    variable = variable.format("Fourth")
    print(variable)
    variable += "\n"
    print(variable, end="")

就这样。

其他回答

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。

PEP 8风格指南建议使用括号:

包装长行的首选方式是在括号、括号和大括号内使用Python的隐含行延续。通过将表达式括在括号中,可以在多行上打断长行。应优先使用这些字符,而不是使用反斜杠作为换行符。

例子:

long_string = (
    "This is a lengthy string that takes up a lot of space. I am going to "
    "keep on typing words to fill up more and more space to show how you can "
    "split the string across multiple lines."
)

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

用\换行对我很有用。下面是一个例子:

longStr = "This is a very long string " \
        "that I wrote to help somebody " \
        "who had a question about " \
        "writing long strings in Python"

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