As stated in PEP8:
Separate top-level function and class definitions with two blank lines.
if __name__ == '__main__':
class Pos:
def __init__(self, x, y):
self.x = x
self.y = y
class Lifetime:
def __init__(self, lifetime):
if lifetime < 0:
raise ValueError('lifetime must be above 0')
self.lifetime = lifetime
class Name:
def __init__(self, name):
self.name = '"' + name + '"'