Exception 例外
例外處理
最簡單
語法:
try:
例外
except:
處理例外
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try:
num1 = 10
num2 = 0
res = num1 / num2
except:
print("出現例外")
出現例外
取得Exception
語法:
try:
例外
except 例外 as 自訂名稱:
處理例外
try:
可能有例外的程式碼
except Exception as e:
取得e例外內容
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try:
num1 = 10
num2 = 0
res = num1 / num2
except Exception as e:
print(f"exception: {e} \n"
"type:", type(e))
exception: division by zero
type: <class 'ZeroDivisionError'>
多個except 與 finally
語法:
try:
例外
except 例外 as 自訂名稱:
處理例外
else:(可省略不寫)
沒有例外發生
finally:(可省略不寫)
不管有沒有例外都執行
注意！以下程式碼，執行到res = num1 / num2就產生例外，之後的open("/目錄/檔案","r")就不會執行。
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try:
num1 = 10
num2 = 0
res = num1 / num2
open("/目錄/檔案","r")
except ZeroDivisionError as e:
print(f"ZeroDivisionError\n")
except Exception as e:
print(f"exception: {e} \n")
finally:
print(f"finally: \n")
ZeroDivisionError
finally:
取得多個except
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try:
num1 = 10
num2 = 0
res = num1 / num2
open("/目錄/檔案","r")
except (ZeroDivisionError,FileNotFoundError) as e:
print(e)
finally:
print(f"finally: \n")
division by zero
finally:
raise
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try:
raise ZeroDivisionError("主動拋出zero例外")
except (ZeroDivisionError,FileNotFoundError) as e:
print(f"exception: {e} type: {type(e)}")
exception: 主動拋出zero例外 type: <class 'ZeroDivisionError'>
如果沒人處理exception 由源頭處理
下方程式碼，f3() 沒有處理exception，返回f2()，但f2()也沒處理exception，返回f1()，由f1()處理。
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def f1():
print("-----f1 start ----")
try:
f2()
except :
print("exception")
print("-----f1 end ----")
def f2():
print("-----f2 start ----")
f3()
print("-----f2 end ----")
def f3():
print("-----f3 start ----")
print(10 / 0)
print("-----f3 end ----")
f1()
-----f1 start ----
-----f2 start ----
-----f3 start ----
exception
-----f1 end ----
Error 種類
IndexError
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try:
str = "Hello"
print(str[100])
except Exception as e:
print(e)
string index out of range
KeyError
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dict1 = {"name":"cici", "age":18}
print(dict1["address"])
TypeError
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try:
a = "Hello"
b = 5
print(a + b)
except Exception as e:
print(e)
can only concatenate str (not "int") to str
ValueError
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try:
print(int("Hello"))
except Exception as e:
print(e)
invalid literal for int() with base 10: 'Hello'
FileNotFoundError
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# /Users/cici/testc/file_test2
try:
f = open("/目錄/檔名", "r", encoding="utf-8")
except Exception as e:
print(e)
[Errno 2] No such file or directory: '/目錄/檔名'
AttributeError
沒有這個屬性
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class A:
def hi(self):
pass
a = A()
print(a.name)