Auto __repr__ method

Question

I want to have simple representation of any class, like { property = value }, is there auto __repr__?

Answer 1

I use this helper function to generate repr s for my classes. It is easy to run in a unittest function, ie.

def test_makeRepr(self):
    makeRepr(Foo, Foo(), "anOptional space delimitedString ToProvideCustom Fields")

this should output a number of potential repr to the console, that you can then copy/paste into your class.

def makeRepr(classObj, instance = None, customFields = None):
    """Code writing helper function that will generate a __repr__ function that can be copy/pasted into a class definition.

    Args:
        classObj (class):
        instance (class):
        customFields (string):

    Returns:
        None:

    Always call the __repr__ function afterwards to ensure expected output.
    ie. print(foo)

    def __repr__(self):
        msg = ""
        attributes = [self.var1, self.var2]
        return msg.format(*attributes)
    """ 
    if isinstance(instance, classObj):
        className = instance.__class__.__name__
    else:
        className=classObj.__name__

    print('Generating a __repr__ function for: ', className,"\n")
    print("\tClass Type: "+classObj.__name__, "has the following fields:")
    print("\t"+" ".join(classObj.__dict__.keys()),"\n")
    if instance:
        print("\tInstance of: "+instance.__class__.__name__, "has the following fields:")
        print("\t"+" ".join(instance.__dict__.keys()),"\n")
    else:
        print('\tInstance of: Instance not provided.\n')

    if customFields:
        print("\t"+"These fields were provided to makeRepr:")
        print("\t"+customFields,"\n")
    else:
        print("\t"+"These fields were provided to makeRepr: None\n")
    print("Edit the list of fields, and rerun makeRepr with the new list if necessary.\n\n")

    print("repr with class type:\n")
    classResult = buildRepr( classObj.__name__, " ".join(classObj.__dict__.keys()))
    print(classResult,"\n\n")

    if isinstance(instance, classObj):
        instanceResult = buildRepr( instance.__class__.__name__, " ".join(instance.__dict__.keys()))
    else:
        instanceResult = "\t-----Instance not provided."
    print("repr with instance of class:\n")
    print(instanceResult,"\n\n") 

    if customFields:
        customResult = buildRepr( classObj.__name__, customFields)
    else:
        customResult = '\t-----Custom fields not provided'
    print("repr with custom fields and class name:\n")
    print(customResult,"\n\n")    

    print('Current __repr__')
    print("Class Object: ",classObj)
    if instance:
        print("Instance: ",instance.__repr__())
    else:
        print("Instance: ", "None")


def buildRepr(typeName,fields):
    funcDefLine = "def __repr__(self):"
    msgLineBase  = '    msg = "<{typename}({attribute})>"'
    attributeListLineBase = '    attributes = [{attributeList}]'
    returnLine = '    return msg.format(*attributes)'
    x = ['self.' + x for x in fields.split()]
    xResult = ", ".join(x)
    y = [x + ' = {}' for x in fields.split()]
    yResult = ', '.join(y)
    msgLine = msgLineBase.format(typename = typeName, attribute = yResult)
    attributeListLine = attributeListLineBase.format(attributeList = xResult) 
    result = "{declaration}\n{message}\n{attributes}\n{returnLine}".format(declaration = funcDefLine,
                                                                       message = msgLine,
                                                                       attributes = attributeListLine,
                                                                       returnLine =returnLine )
    return result