Spliting Python string interpolation onto multiple lines

Question

I've got a logging statement, something like:

get_logger().info(
    'Logger logging %s because we need to log it.' % response['foo']['bar']
)

With indentation it comes out well over 80 rows. If I could split it around the %, it would be fine.

How can I split this into multiple lines. (ideally without just putting response['foo']['bar'] into a variable)

Put a `(` after the `%` - put the stuff on the next line and add a `)` ? — Jon Clements, Aug 18 '17 at 19:00

Ivan Chaer · Accepted Answer · 2017-08-19T12:25:11.437

1

get_logger().info(
    'Logger logging %s because we need to log it.' 
    % response['foo']['bar']
)

edited Aug 19 '17 at 12:25

answered Aug 18 '17 at 19:06

Ivan Chaer

6,980
1
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48

Thanks, I guess that should have been obvious, but I'm pretty new to Python. – Jones Aug 18 '17 at 19:15

score 0 · Answer 2 · answered Aug 18 '17 at 19:32

When using Python string formatting functionalities you can provide a tuple, not just a single value, as an input:

>>> "%d %d %d" % tuple(range(3)) # or just (0, 1, 2)
'0 1 2'

And then easily split your input tuple into multiple lines. You may, additionally, even assign the template string with percent-suffixed placeholders to a variable and use it later. An example would be:

>>> template = "The averaged temperatures of the last three days were %d, %d and %d"
>>> template % (22, 26, 23)
'The averaged temperatures of the last three days were 22, 26 and 23'

You can know more about Python string formatting in printf-style String Formatting (Python 3.5.4).

score 0 · Answer 3 · answered Nov 17 '17 at 19:14

It might be worth noting that, for logging,

get_logger().info(
    'Logger logging %s because we need to log it.' 
    % response['foo']['bar']
)

is the same as:

get_logger().info(
    'Logger logging %s because we need to log it.', 
    response['foo']['bar']
)

since the debug(), info(), etc . methods interpret *args as to be used for string formatting the message.

https://docs.python.org/2/library/logging.html#logging.Logger.debug

In general for long strings, ones that ought to wrap around column 80, use parentheses, taking advantage of python's built-in string joining:

deeplyNested = True
thing = 'feedback'
class Contrived(object):
    def __init__(self):
        if deeplyNested:
            logger.info(
                ("Sometimes there's a lot to say in %s and you need to write"
                 " longer messages than what nicely fits in the 80 column"
                 " limit."),
                thing
            )

Spliting Python string interpolation onto multiple lines

3 Answers3