When to use %r instead of %s in Python? [duplicate]
The %s
specifier converts the object using str()
, and %r
converts it using repr()
.
For some objects such as integers, they yield the same result, but repr()
is special in that (for types where this is possible) it conventionally returns a result that is valid Python syntax, which could be used to unambiguously recreate the object it represents.
Here's an example, using a date:
>>> import datetime>>> d = datetime.date.today()>>> str(d)'2011-05-14'>>> repr(d)'datetime.date(2011, 5, 14)'
Types for which repr()
doesn't produce Python syntax include those that point to external resources such as a file
, which you can't guarantee to recreate in a different context.
Use the %r
for debugging, since it displays the "raw" data of the variable, but the others are used for displaying to users.
That's how %r
formatting works; it prints it the way you wrote it (or close to it). It's the "raw" format for debugging. Here \n
used to display to users doesn't work. %r
shows the representation if the raw data of the variable.
months = "\nJan\nFeb\nMar\nApr\nMay\nJun\nJul\nAug"print "Here are the months: %r" % months
Output:
Here are the months: '\nJan\nFeb\nMar\nApr\nMay\nJun\nJul\nAug'
Check this example from Learn Python the Hard Way.
%r
shows with quotes:
It will be like:
I said: 'There are 10 types of people.'.
If you had used %s
it would have been:
I said: There are 10 types of people..