str() vs repr() in Python

In Python, the str() and repr() functions are used to obtain string representations of objects. While they may seem similar at first glance, there are some differences in how they behave. Both of the functions can be helpful in debugging or printing useful information about the object.

Python str()

In the given example, we are using the str() function on a string and floating values in Python.

s = 'Hello, Geeks.'
print (str(s))
print (str(2.0/11.0))

Output:

Hello, Geeks.
0.181818181818

Python repr()

In the given example, we are using the repr() function on a string and floating values in Python.

s = 'Hello, Geeks.'
print (repr(s))
print (repr(2.0/11.0))

Output:

'Hello, Geeks.'
0.18181818181818182

str() vs repr() in Python Examples

From the above output, we can see if we print a string using the repr() function then it prints with a pair of quotes and if we calculate a value we get a more precise value than the str() function.

Python __str__() and __repr__() with  a Built-In Class

In this example, we are creating a DateTime object of the current time and we are printing it into two different formats.

str() displays today's date in a way that the user can understand the date and time. repr() prints an “official" representation of a date-time object (means using the “official” string representation we can reconstruct the object).

import datetime
today = datetime.datetime.now()

# Prints readable format for date-time object
print(str(today))

# prints the official format of date-time object
print(repr(today))

Output :

2016-02-22 19:32:04.078030
datetime.datetime(2016, 2, 22, 19, 32, 4, 78030)

How to make them work for our own defined classes? 

A user-defined class should also have a __repr__() if we need detailed information for debugging. And if we think it would be useful to have a string version for users, we create a __str__() function. In this example, We have created a class Complex which has two instance variables real and imag. We are creating custom __repr__() and __str__() methods in the class.

# Python program to demonstrate writing of __repr__ and
# __str__ for user defined classes

# A user defined class to represent Complex numbers
class Complex:

    # Constructor
    def __init__(self, real, imag):
    self.real = real
    self.imag = imag

    # For call to repr(). Prints object's information
    def __repr__(self):
    return 'Rational(%s, %s)' % (self.real, self.imag)    

    # For call to str(). Prints readable form
    def __str__(self):
    return '%s + i%s' % (self.real, self.imag)    


# Driver program to test above
t = Complex(10, 20)

# Same as "print t"
print (str(t))
print (repr(t))

Output :

10 + i20
Rational(10, 20)

Difference between Python str() and Python repr()

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