python之異常處理

下面的例子可以方便的理解異常處理的流程：

sep = '

-' * 32 + '\n'
print(sep + '
exception raised and caught')
try:
x = '
spam
'[9]
except
indexerror:
print('
except run')
finally
:    
print('
finally run')
print('
after run')
print(sep + '
no exception raised')
try:
x = '
spam
'[3]
except
indexerror:
print('
except run')
finally
:    
print('
finally run')
print('
after run')
print(sep + '
no exception raised, with else')
try:
x = '
spam
'[3]
except
indexerror:
print('
except run')
else
:    
print('
else run')
finally
:    
print('
finally run')
print('
after run')
print(sep + '
exception raised but not caught')
try:
x = 1 /0
except
indexerror:
print('
except run')
finally
:    
print('
finally run')
print('
after run
')

輸出：

traceback (most recent call last):

--------------------------------file 
"f:/xhbproject/fenci_test/cdn-api/test.py
", line 36, in
exception raised and caught
except
runfinally
run    x = 1 /0
after run
zerodivisionerror: division by zero
--------------------------------no exception raised
finally
runafter run
--------------------------------no exception raised, with else
else
runfinally
runafter run
--------------------------------exception raised but not caught
finally run

else子句是在沒有發生異常的情況下執行的，finally子句是不管有沒有異常都會執行，try語句塊後的語句是在沒有異常或異常被程式捕獲處理後才會執行。

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