How to define the str function while using type to create a class?

Question

I am trying to achieve the following case:

    class ABCD(object):
        def __str__(self): 
            return "some string"

    a=ABCD()
    print a
    some string

Using type:

    A=type("A",(object,),dict(__str__="some string",h=5))
    a=A()
    print a

But get the following error:

    Traceback (most recent call last):
    File "<stdin>", line 1, in <module>
    TypeError: 'str' object is not callable

... it needs to be a function not a string

juanpa.arrivillaga
– juanpa.arrivillaga

2018-01-12 19:50:04 +00:00
Commented Jan 12, 2018 at 19:50 — juanpa.arrivillaga
– juanpa.arrivillaga, Commented Jan 12, 2018 at 19:50

cs95 · Accepted Answer · 2018-01-12 19:55:31Z

4

Did you mean to pass a callback? __str__ is to be implemented as an instance method that returns a string.

A = type("A",(object,), dict(__str__=lambda self: "some string" , h=5))
a = A()

print(a)
some string

When you call print on an object, its __str__ method is called. If the object does not have one defined, the the __str__ for the object class is invoked. So, you shouldn't assign a string to __str__ because python'll try to "call" it as a function, throwing a TypeError.

edited Jan 12, 2018 at 19:55

answered Jan 12, 2018 at 19:50

cs95

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