Python:non-empty format string passed to object.format

Question

images_name = "%s/%03d_image.jpg" % (target, i)

I have formatted it to images_name = '{:03d_image.jpg}'.format((target, i))

Could you please point me out the mistake?

Also can this be formatted in a better manner?

format_str = ('%s: Step %d, Loss = %.2f (%.1f examples/sec; %.3f ' 'sec/batch)')

print(format_str % (datetime.now(), step, loss_value,examples_per_sec, duration))

Moses Koledoye · Accepted Answer · 2017-08-30 08:19:29Z

1

You should specify separate placeholders just like you've done with the old-format style and not include parts that do not need formatting within the curly braces:

images_name = '{}/{:03d}_image.jpg'.format(target, i)

The same rule applies to the second string:

format_str = '{}: Step {:d}, Loss = {:.2f} ({:.1f} examples/sec; {:.3f} sec/batch)'
print(format_str.format(datetime.now(), step, 
                        loss_value, examples_per_sec, duration))

Read more about the old and new format specifications in Python.

edited Aug 30, 2017 at 8:19

answered Aug 30, 2017 at 8:13

Moses Koledoye

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