python - abnormal program and debug (exception handling)

First, exception handling

For a block of statements at run time may be wrong, you can design a good problem occurs after earlier solutions,

Or the corresponding prompt information. Use try ... except statement to handle exceptions thrown Python:

 

----------------------------------------- # 
# exception catching 
# ---- ------------------------------------- 
# using the pass statement except statement, ignore the exception occurred 
list1 = [ '100', ' 200', ' three hundred', 'four hundred', '500'] 
Total = 0 
for E in List1: 
    the try: 
        Total = Total + int (E) 
    the except: 
        Pass 
Print (Total) 

# file does not exist 
the try: 
    file = Open ( "config.txt", "r") 
the except FileNotFoundError: 
    ( "! file does not exist") Print 


# user presses Ctrl + keyboard interrupt exception thrown when the C key combination 
pwd = 888 # password 
num = -1 # password 
times = 0 # wrong passwords are entered 
the while NUM = pwd:! 
    the try: 
        NUM = int (the iNPUT ( "Please enter the three-digit password: "))
    the except ValueError: 
        print ( "Make sure you enter is the number!") 
        the Continue 
    the except: # universal exception caught 
        print ( "Exit") 
        BREAK 

    IF NUM = pwd:! 
        print ( "! Wrong password") 
        Times + = 1 
        IF Times> 3 =: 
            Print ( "wrong password more than 3 times, please try again tomorrow!") 
            BREAK 
        the else: 
            the Continue 
    the else: 
        ( "! password is correct") Print 
the else: 
    Print ( "! Login successful") 


# uses raise initiative thrown 
zero_div DEF (): 
    the X-100 = 
    the y-0 = 
    IF the y-== 0: 
        # Once an exception is thrown, and did not do the appropriate exception caught, this program will quit. 
        raise ZeroDivisionError ( "divisor can not be 0!"

    Print (z) 


# zero_div () 
try: 
    zero_div () 
the except ZeroDivisionError: 
    Print ( "to capture a ZeroDivisionError abnormal!") 
else: # only try normal circumstances, the statement will be executed else 
    Print ( "test1") 
a finally: # whether it is normal or abnormal will execute the statement 
    Print ( "test2") 

# If you throw a SystemExit exception will force the end of the run Python interpreter 
raise SystemExit

----------------------------------------- # 
# custom exception 
# --- -------------------------------------- 
class ExitLoop (Exception): 
    Pass 


the try: 
    X =. 1 
    X the while <. 5: 
        for Y in Range (. 1,. 5): 
            Print (X, Y) 

            IF (X ==. 3) and (Y ==. 3): 
                # by throwing an exception, directly out nested loop 
                The raise ExitLoop 

            X + =. 1 
the except ExitLoop: 
    Print ( ". 3, Y =. 3 from bounce when x = nested loop") 


class the CustomError (Exception): 
    DEF the __init __ (self, ERR = 'custom error'): 
        Exception .__ init__ (Self, ERR) 


The raise CustomError