Art Zemon's Blog Posts

Yesterday, I spent longer than I care to admit debugging an update to an old PHP script. It fetched a string from a MySQL database and (here’s the new part) passed the string to json_encode(). That call failed when the data included the multibyte characters ¼ or ½ or ¾. All of my attempts to remove the multibyte […]

I needed a singleton database class in a Python 2.7 program and wrote it this way. class Singleton(type): _instances = {} def __call__(cls, *args, **kwargs): if cls not in cls._instances: cls._instances[cls] = super(Singleton, cls).__call__(*args, **kwargs) return cls._instances[cls] class Database(): __metaclass__ = Singleton def __init__(self): self.db = MySQLdb.connect(…) I like this pattern but I realized that […]

Following onto yesterday’s post about Python Properties and @property, there is a neat little trick to create a read-only property of a Python class. All you have to do is omit the setter. This Hero class has a read-write property “name” class Hero(object): def __init__(self, **kwargs): self.name = kwargs[‘name’] @property def name(self): return ‘%s %s’ % […]

My son pointed me at PyCharm and, while poking through it’s built-in “intentions,” I discovered Python’s @property decorator, which led me to learn more about the Pythonic way to handle class properties. Unlike Java and C++, Python encourages you to create public class attributes (a/k/a properties). Here is an example: class Hero(object): def __init__(self, **kwargs): […]