Metaclasses in python

metaclasses.py

# Create classes based on csv file data
with open("file.csv", 'r') as f:
    header = f.readline().split(',')
    metaclass = type('csv', (object,), {h:None for h in header})
    for line in f.readlines():
        m = metaclass()
        line = line.split(',')
        for i in range(len(header)):
            setattr(m, header[i], line[i])
        yield m # Return as generator
        
# These are equivilent definitions
class X:                                                      
  a = 1                                                     
  def hello(self, k):
      return k
a = type('Y', (object,), {'a':1, 'hello':lambda self, k: k})
print(a().hello('hello from a metaclass'))

# This is equivilent to X(), instances are created with __new__,
# which returns an instance to be initated by __init__. 
x = object.__new__(X)
if type(x) == X: # If X were a factory class it wouldn't make sense to call __init__() on it. 
    x.__init__()