可能觸發(fā)異常產(chǎn)生的代碼會放到try語句塊里，而處理異常的代碼會在except語句塊里實現(xiàn)。例如：

try: file = open(‘test.txt’, ‘rb’)except IOError as e: print(‘An IOError occurred. {}’.format(e.args[-1]))

我們可以使用三種方法來處理多個異常。

第一種方法需要把所有可能發(fā)生的異常放到一個元組里。像這樣：

try: file = open(‘test.txt’, ‘rb’)except (IOError, EOFError) as e: print(“An error occurred. {}”.format(e.args[-1]))

另外一種方式是對每個單獨的異常在單獨的except語句塊中處理。我們想要多少個except語句塊都可以：

try: file = open(‘test.txt’, ‘rb’)except EOFError as e: print(“An EOF error occurred.”) raise eexcept IOError as e: print(“An error occurred.”) raise e

最后一種方式會捕獲所有異常：

try: file = open(‘test.txt’, ‘rb’)except Exception as e: # Some logging if you want raise e

注意，捕獲所有異常可能會造成意外的結(jié)果，比如，通常我們使用CTRL+C來終止程序，但如果程序中捕獲了所有異常，CTRL+C就無法終止程序了。

包裹到finally從句中的代碼不管異常是否觸發(fā)都將會被執(zhí)行。這可以被用來在腳本執(zhí)行之后做清理工作：

try: file = open(‘test.txt’, ‘rb’)except IOError as e: print(‘An IOError occurred. {}’.format(e.args[-1]))finally: print(“This would be printed whether or not an exception occurred!”)# Output: An IOError occurred. No such file or directory# This would be printed whether or not an exception occurred!

如果想在沒有觸發(fā)異常的時候執(zhí)行一些代碼，可以使用else從句。

有人也許問了：如果你只是想讓一些代碼在沒有觸發(fā)異常的情況下執(zhí)行，為啥你不直接把代碼放在try里面呢？回答是，那樣的話這段代碼中的任意異常都還是會被try捕獲，而你并不一定想要那樣。

try: print(‘I am sure no exception is going to occur!’)except Exception: print(‘exception’)else: # any code that should only run if no exception occurs in the try, # but for which exceptions should NOT be caught print(‘This would only run if no exception occurs. And an error here ‘ ‘would NOT be caught.’)finally: print(‘This would be printed in every case.’)# Output: I am sure no exception is going to occur!# This would only run if no exception occurs. And an error here would NOT be caught# This would be printed in every case.

else從句只會在沒有異常的情況下執(zhí)行，而且它會在finally語句之前執(zhí)行。