IndexError while calling dunder methods-CodePudding

I want to print the values from the dunder methods of a class foo. However, I got the error:

IndexError: Replacement index 1 out of range for positional args tuple

The code snippet is as follows:

class foo(object):
    def __str__(self):
        return 'Testing'
        
    def __repr__(self):
        return 'Programming'
    
print('{}{}'.format(foo()))

CodePudding user response：

Your template string has two placeholders while you pass only one value in the .format() call. .format() will only execute __str__, not __repr__. You should either use

print('{}'.format(foo()))

my_foo = foo()
print('{}{}'.format(my_foo, repr(my_foo)))

As a side note, class names should be in title case (Foo) per PEP-8.

CodePudding user response：

I did the following and it gave me the desired output.

class foo (object):
    def __str__(self):
        return 'Testing'
        
    def __repr__(self):
        return 'Programming'
    
print('{0!s}{0!r}'.format(foo(),repr(foo)))

Output:

TestingProgramming