Understanding difference between Double Quote and Single Quote with __repr__()

Question

What is the difference between print, object, and repr()? Why is it printing in different formats?

See the output difference:

>>> x="This is New era"
>>> print x             # print in double quote when with print()
This is New era

>>> x                   #  x display in single quote
'This is New era'

>>> x.__repr__()        # repr() already contain string
"'This is New era'"

>>> x.__str__()         # str() print only in single quote ''
'This is New era'

Frag

I think the name x is attached to 'This is New era' string. When I called for example repr(x) the iterpreter puts 'This is New era' instead of x and then called repr('This is New era'). – Frag

Answer 1

There is no semantic difference between ' and ". You can use ' if the string contains " and vice versa, and Python will do the same. If the string contains both, you have to escape some of them (or use triple quotes, """ or '''). (If both ' and " are possible, Python and many programmers seem to prefer ', though.)

>>> x = "string with ' quote"
>>> y = 'string with " quote'
>>> z = "string with ' and \" quote"
>>> x
"string with ' quote"
>>> y
'string with " quote'
>>> z
'string with \' and " quote'

About print, str and repr: print will print the given string with no additional quotes, while str will create a string from the given object (in this case, the string itself) and repr creates a "representation string" from the object (i.e. the string including a set of quotes). In a nutshell, the difference between str and repr should be that str is easy to understand for the user and repr is easy to understand for Python.

Also, if you enter any expression in the interactive shell, Python will automatically echo the repr of the result. This can be a bit confusing: In the interactive shell, when you do print(x), what you see is str(x); when you use str(x), what you see is repr(str(x)), and when you use repr(x), you see repr(repr(x)) (thus the double quotes).

>>> print("some string") # print string, no result to echo
some string
>>> str("some string")   # create string, echo result
'some string'
>>> repr("some string")  # create repr string, echo result
"'some string'"

Northeastwards

I think the name x is attached to 'This is New era' string. When I called for example repr(x) the iterpreter puts 'This is New era' instead of x and then called repr('This is New era'). – Frag

__repr__ is usually constructed in such a way, that when you pass its return value to eval, you would receive the exact same object __repr__ was defined on in the first place. Hence the double quotes around the single-quoted string, as eval("'My string'") would work, but eval('my string') would raise a SyntaxError. See also here – Antibiosis

yeah @Antibiosis ...... eval calculates the result of an expression. The result is always a value (such as a number, a string, or an object) – Frag

Answer 2

See __repr__:

Called by the repr() built-in function and by string conversions (reverse quotes) to compute the “official” string representation of an object. If at all possible, this should look like a valid Python expression that could be used to recreate an object with the same value (given an appropriate environment).

And __str__:

Called by the str() built-in function and by the print statement to compute the “informal” string representation of an object. This differs from __repr__() in that it does not have to be a valid Python expression: a more convenient or concise representation may be used instead.

Emphasis added by me.

Huck

Answer 3

__str__ and __repr__ are both methods for getting a string representation of an object. __str__ is supposed to be shorter and more user-friendly, while __repr__ is supposed to provide more detail.

However, in python there is no difference between single quote and double quote.

Tieback