try:
  int("x")
except Exception as e:
  '''异常的父类，可以捕获所有的异常'''
  print(e)
# e变量是Exception类型的实例，支持__str__()方法，可以直接打印。 
invalid literal for int() with base 10: 'x'
try:
  int("x")
except Exception as e:
  '''异常的父类，可以捕获所有的异常'''
  print(e.args)

# e变量有个属性是.args，它是错误信息的元组

("invalid literal for int() with base 10: 'x'",)try: datetime(2017,2,30)except ValueError as e: print(e) day is out of range for monthtry: datetime(22017,2,30)except ValueError as e: print(e) year 22017 is out of rangetry: datetime(2017,22,30)except ValueError as e: print(e) month must be in 1..12e = Nonetry: datetime(2017,22,30)except ValueError as e: print(e) month must be in 1..12e
# e这个变量在异常过程结束后即被释放，再调用也无效
 Traceback (most recent call last): File "<input>", line 1, in <module>NameError: name 'e' is not defined

errarg = None
try:
  datetime(2017,22,30)
except ValueError as errarg:
  print(errarg)
  
month must be in 1..12
errarg
Traceback (most recent call last):
 File "<input>", line 1, in <module>
NameError: name 'errarg' is not defined
try:
  datetime(2017,22,30)
except ValueError as errarg:
  print(errarg.args)

# ValueError.args 返回元组

('month must be in 1..12',)
message = None
try:
  datetime(2017,22,30)
except ValueError as errarg:
  print(errarg.args)
  message = errarg.args
  
('month must be in 1..12',)
message
('month must be in 1..12',)
try:
  datetime(2017,22,30)
except ValueError as errarg:
  print(errarg.args)
  message = errarg
  
('month must be in 1..12',)
message
ValueError('month must be in 1..12',)
str(message)
'month must be in 1..12'

try:
  y = 2017
  m = 22
  d = 30
  datetime(y,m,d)
except ValueError as errarg:
  print(errarg.args)
  message = errarg
  m = re.search(u"month", str(message))
  if m:
    dt = datetime(y,1,d)
    
('month must be in 1..12',)
dt
datetime.datetime(2017, 1, 30, 0, 0)

def validatedate(y, mo, d):
  dt = None
  try:
    dt = datetime(y, mo, d)
  except ValueError as e:
    print(e.args)
    print(str(y)+str(mo)+str(d))
    message = e
    ma = re.search(u"^(year)|(month)|(day)", str(message))
    ymd = ma.groups()
    if ymd[0]:
      dt = validatedate(datetime.now().year, mo, d)
    if ymd[1]:
      dt = validatedate(y, datetime.now().month, d)
    if ymd[2]:
      dt = validatedate(y, mo, datetime.now().day)
  finally:
    return dt 
validatedate(20199, 16, 33)
('year 20199 is out of range',)
('month must be in 1..12',)
('day is out of range for month',)
datetime.datetime(2018, 4, 20, 0, 0)