Обработка исключений, создание класса исключения на Python

class MyError(Exception):
    def __init__(self,text):
        MyError.txt = text
 
a = input("Input positive integer: ")
 
try:
    a = int(a)
    if a < 0:
        raise MyError("you give negative!") # возбуждает собственное исключение
except ValueError:
    print("Error type of value!")
except MyError:
    print(MyError.txt)
 
print(a)

class General: pass
class Specific1(General): pass
class Specific2(General): pass
 
def raiser0():
    x = General()
    raise x
 
def raiser1():
    x = Specific1()
    raise x
 
def raiser2():
    x = Specific2()
    raise x
 
for func in (raiser0, raiser1, raiser2):
    try:
        func()
    except General:
        import sys
        print(sys.exc_info()[0])