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Python try/except/finally等
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Python try/except/finally等
[代碼塊] x?=?'abc'??def?fetcher(obj,?index):??????return?obj[index]????fetcher(x,?4)??輸出：
??File?"test.py",?line?6,?in?<module>??????fetcher(x,?4)????File?"test.py",?line?4,?in?fetcher??????return?obj[index]??IndexError:?string?index?out?of?range??
第一：?try不僅捕獲異常，而且會(huì)恢復(fù)執(zhí)行
def?catcher():??????try:??????????fetcher(x,?4)??????except:??????????print?"got?exception"??????print?"continuing"?? 輸出：
got?exception??continuing??
第二：無論try是否發(fā)生異常，finally總會(huì)執(zhí)行
def?catcher():??????try:??????????fetcher(x,?4)??????finally:??????????print?'after?fecth'?? 輸出：
after?fecth??Traceback?(most?recent?call?last):????File?"test.py",?line?55,?in?<module>??????catcher()????File?"test.py",?line?12,?in?catcher??????fetcher(x,?4)????File?"test.py",?line?4,?in?fetcher??????return?obj[index]??IndexError:?string?index?out?of?range??
第三：try無異常，才會(huì)執(zhí)行else
def?catcher():??????try:??????????fetcher(x,?4)??????except:??????????print?"got?exception"??????else:??????????print?"not?exception"?? 輸出：
got?exception?? def?catcher():??????try:??????????fetcher(x,?2)??????except:??????????print?"got?exception"??????else:??????????print?"not?exception"?? 輸出：
not?exception?? else作用：沒有else語句，當(dāng)執(zhí)行完try語句后，無法知道是沒有發(fā)生異常，還是發(fā)生了異常并被處理過了。通過else可以清楚的區(qū)分開。
?
第四：利用raise傳遞異常
def?catcher():??????try:??????????fetcher(x,?4)??????except:??????????print?"got?exception"??????????raise?? 輸出：
got?exception??Traceback?(most?recent?call?last):????File?"test.py",?line?37,?in?<module>??????catcher()????File?"test.py",?line?22,?in?catcher??????fetcher(x,?4)????File?"test.py",?line?4,?in?fetcher??????return?obj[index]??IndexError:?string?index?out?of?range?? raise語句不包括異常名稱或額外資料時(shí)，會(huì)重新引發(fā)當(dāng)前異常。如果希望捕獲處理一個(gè)異常，而又不希望
異常在程序代碼中消失，可以通過raise重新引發(fā)該異常。
?
第五：except(name1, name2)
def?catcher():??????try:??????????fetcher(x,?4)??????except(TypeError,?IndexError):??????????print?"got?exception"??????else:??????????print?"not?exception"?? 捕獲列表列出的異常，進(jìn)行處理。若except后無任何參數(shù)，則捕獲所有異常。
def?catcher():??????try:??????????fetcher(x,?4)??????except: ?
轉(zhuǎn)載于:https://www.cnblogs.com/jp927/p/4535416.html
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