Dynamically creating classes in python and __repr__

Question

This is a fairly simple question, I hope you can all enlighten me. In the example below, how can I define __repr__ for a dynamic job on self.name?

Thanks everyone!

import re inputlist = 'Project="Sparcy" Desc=""\nProject="Libs" Desc=""\nProject="Darwin" Desc=""\nProject="Aaple" Desc="The big project"' regex = re.compile('([^ =]+) *= *("[^"]*"|[^ ]*)') results = [] for project in inputlist.split("\n"): items = [ (k.strip(), v.strip()) for k, v in regex.findall(project)] if len(items) < 2: print("Houston we have a problem - Only %sk/v pair found for %s" % (len(items), project)) continue item_dict = dict(items[1:]) item_dict['name'] = items[0][1] klass = type(items[0][0], (object,), item_dict) results.append(klass) print results 

What I'm looking for is

psuedo code

 for result in results type(result) → Project print result → Sparky 

Answer 1

I guess you want

 print results 

for return

 ["Sparcy", "Libs", "Darwin", "Aaple"] 

• Printing a list shows a representation of its elements.
• repr(elt) is defined by type(elt).__repr__ .
• Since in this case the elements are classes, you need to set __repr__ for the class type.

---

 import re inputlist = '''\ Project="Sparcy" Desc="" Project="Libs" Desc="" Project="Darwin" Desc="" Project="Aaple" Desc="The big project" Site="Phoenix" Protocol="Cheese"''' regex = re.compile('([^ =]+) *= *("[^"]*"|[^ ]*)') results = [] for project in inputlist.split("\n"): items = [ (k.strip(), v.strip()) for k, v in regex.findall(project)] if len(items) < 2: print("Houston we have a problem - Only %sk/v pair found for %s" % (len(items), project)) continue item_dict = dict(items[1:]) item_dict['name'] = items[0][1] projectname=items[0][0] metametaklass=type('meta_'+projectname,(type,),{'__repr__':lambda cls: cls.__name__}) metaklass=metametaklass(projectname,(type,),{'__repr__':lambda cls: cls.name}) klass=metaklass(projectname+'_class', (object,), item_dict) results.append(klass) print(results) 

gives

 ["Sparcy", "Libs", "Darwin", "Aaple", "Phoenix"] 

and

 for result in results: print(type(result)) print(result) print('-'*80) 

gives

 Project "Sparcy" -------------------------------------------------------------------------------- Project "Libs" -------------------------------------------------------------------------------- Project "Darwin" -------------------------------------------------------------------------------- Project "Aaple" -------------------------------------------------------------------------------- Site "Phoenix" -------------------------------------------------------------------------------- 

PS. Note that this is a perversion of __repr__ , since the repr object of the object must be an unambiguous string representation of the object. That is, it is assumed that enough information is available to reproduce the object. You should probably define another print function instead of messing with metaclasses.