What is the meaning of %r?
Solution 1
Background:
In Python, there are two builtin functions for turning an object into a string: str
vs. repr
. str
is supposed to be a friendly, human readable string. repr
is supposed to include detailed information about an object's contents (sometimes, they'll return the same thing, such as for integers). By convention, if there's a Python expression that will eval to another object that's ==, repr
will return such an expression e.g.
>>> print repr('hi') 'hi' # notice the quotes here as opposed to... >>> print str('hi') hi
If returning an expression doesn't make sense for an object, repr
should return a string that's surrounded by < and > symbols e.g. <blah>
.
To answer your original question:
In addition:
You can control the way an instance of your own classes convert to strings by implementing __str__
and __repr__
methods.
class Foo:
def __init__(self, foo):
self.foo = foo
def __eq__(self, other):
"""Implements ==."""
return self.foo == other.foo
def __repr__(self):
# if you eval the return value of this function,
# you'll get another Foo instance that's == to self
return "Foo(%r)" % self.foo
Solution 2
It calls repr()
on the object and inserts the resulting string.
Solution 3
It prints the replacement as a string with repr()
.
Solution 4
Adding to the replies given above, '%r'
can be useful in a scenario where you have a list with heterogeneous data type.
Let's say, we have a list = [1, 'apple' , 2 , 'r','banana']
Obviously in this case using '%d'
or '%s'
would cause an error. Instead, we can use '%r'
to print all these values.
Solution 5
The difference between %r
and %s
is, %r
calls the repr()
method and %s
calls the str()
method. Both of these are built-in Python functions.
The repr()
method returns a printable representation of the given object.
The str()
method returns the "informal" or nicely printable representation of a given object.
In simple language, what the str()
method does is print the result in a way which the end user would like to see:
name = "Adam"
str(name)
Out[1]: 'Adam'
The repr()
method would print or show what an object actually looks like:
name = "Adam"
repr(name)
Out[1]: "'Adam'"
photon
Updated on July 05, 2022Comments
-
photon about 2 years
What's the meaning of
%r
in the following statement?print '%r' % (1)
I think I've heard of
%s
,%d
, and%f
but never heard of this. -
dan almost 10 yearsI've found %r to be useful for printing a string of unknown encoding, when otherwise an error can get thrown with %s