Question

I have a function that takes an opened file object file and writes data to it like so:

def Write(self, file):
    file.write("Data")

Now I would like to test that function and I thought it would be neat to do that with some kind of stream that is not writing data to a file. I could not find a Python2.7 class that does the job except the StringIO class. However, in Python2.7 this class expects a unicode string in the write function. (file.write(u"Data")) So I cannot test my Write function with the StringIO class.
In my workaround I created a little dummy class

class MyStream(object):
    S = property(lambda self: self._S)

    def __init__(self):
        self._S = ""

    def write(self, s):
        self._S += s

with which I can now successfully test my Write function.

My question:
Is there a native python class that does the same trick?
Thx in advance for any suggestions
Regards Woltan

Answer 1

As the documentation of io states:

Since this module has been designed primarily for Python 3.x, you have to be aware that all uses of “bytes” in this document refer to the str type (of which bytes is an alias), and all uses of “text” refer to the unicode type. Furthermore, those two types are not interchangeable in the io APIs.

I.e. if you use the backported Python 3 IO library, you have to use unicode. However, the original StringIO class – which considers bytes (Python 2 strings) text and accepts them – still exists in Python 2.7, it’s just not in the backported io. Instead, it has its own module, also called StringIO.