Time for action creating instances
The next method we look at is the constructor the __init__()
method. It will be used to create individual instances of an entity. The constructor can be called in two ways:
- With a single
id
argument, in which case, an existing record will be retrieved from the database and the instance initialized with the column values of this record, or - With a number of keyword arguments to create a new instance and save this as a new database record
The code to implement this behavior looks like the following:
Chapter5/entity.py
def __init__(self,id=None,**kw):
for k in kw:
if not k in self.__class__.columns :
raise KeyError("unknown column") cursor=self.threadlocal.connection.cursor() if id: if len(kw): raise KeyError("columns ...
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