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I have failed to find documentation for the operator % as it is used on strings in Python. What does this operator do when it is used with a string on the left hand side?

BeeOnRope
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Ram Rachum
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4 Answers4

40

It's the string formatting operator. Read up on string formatting in Python.

format % values

Creates a string where format specifies a format and values are the values to be filled in.

phyatt
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Konrad Rudolph
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10

It applies printf-like formatting to a string, so that you can substitute certain parts of a string with values of variables. Example

# assuming numFiles is an int variable
print "Found %d files" % (numFiles, )

See the link provided by Konrad

Diaa Sami
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8

Note that starting from Python 2.6, it's recommended to use the new str.format() method:

>>> "The sum of 1 + 2 is {0}".format(1+2)
'The sum of 1 + 2 is 3'

If you are using 2.6, you may want to keep using % in order to remain compatible with older versions, but in Python 3 there's no reason not to use str.format().

Bastien Léonard
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    format() is really powerful too. You can use named tags like "Hello {planet}".format(planet='earth') – aehlke Aug 06 '09 at 14:27
  • what does the 0 inside the {} do? this line of code seemingly runs the same without it – Wizard Apr 29 '21 at 19:15
6

The '%' operator is used for string interpolation. Since Python 2.6 the String method "format" is used insted. For details see http://www.python.org/dev/peps/pep-3101/