如何在python中将实例转换为String类型？

Question

say class instance is printHello for class Hello
Now when I execute below code
print printHello
The output is "HelloPrinted"
Now I want to compare the printHello with a string type and cannot achieve it because printHello is of type instance. Is there a way to capture the output of print printHello code and use it for comparison or convert the type of printHello to string and I can use it for other string comparisons? Any help is appreciated.

Answer 1

If you want to specifically compare to strings you could do it in two different ways. First is to define the __str__ method for your class:

class Hello:
    def __init__(self, data="HelloWorld"):
        self._data = data
    def __str__(self):
        return self._data

Then you can compare to a string with:

h = Hello()
str(h) == "HelloWorld"

Or you could specifically use the __eq__ special function:

class Hello:
    def __init__(self, data="HelloWorld"):
        self._data = data
    def __str__(self):
        return self._data
    def __eq__(self, other):
        if isinstance(other, str):
            return self._data == other
        else:
            # do some other kind of comparison

then you can do the following:

h = Hello()
h == "HelloWorld"

Answer 2

Either define str or repr in Hello class

More information here - https://docs.python.org/2/reference/datamodel.html#object. str

Answer 3

A special method __repr__ should be defined in your class for this purpose:

class Hello:
    def __init__(self, name):
        self.name= name

    def __repr__(self):
        return "printHello"

Answer 4

I think you want:

string_value = printHello.__str__()

if string_value == "some string":
  do_whatever()

The __str__() method is used by print to make sense of class objects.