最后 Python 中的关键词
先决条件:异常处理、尝试并除 Python 中的
在编程中，可能会出现当前方法在处理一些异常时终止的情况。但是该方法在终止之前可能需要一些额外的步骤，比如关闭文件或网络等等。
所以，为了处理这些情况，Python 提供了一个关键字 finally ，总是在 try和except 块之后执行。 finally 块总是在试块正常终止后或试块因某种异常终止后执行。
语法:
try:
# Some Code....
except:
# optional block
# Handling of exception (if required)
finally:
# Some code .....(always executed)
要点–
- 最后块总是在离开尝试语句后执行。如果某个异常不是由 except 块处理的，它将在 finally 块执行后重新引发。
- 最后块用于释放系统资源。
- 在尝试之后，可以不使用而使用最后使用,除了块，但在这种情况下不会处理任何异常。
示例#1:
# Python program to demonstrate finally
# No exception Exception raised in try block
try:
k = 5//0 # raises divide by zero exception.
print(k)
# handles zerodivision exception
except ZeroDivisionError:
print("Can't divide by zero")
finally:
# this block is always executed
# regardless of exception generation.
print('This is always executed')
输出:
Can't divide by zero
This is always executed
例 2:
# Python program to demonstrate finally
try:
k = 5//1 # No exception raised
print(k)
# intends to handle zerodivision exception
except ZeroDivisionError:
print("Can't divide by zero")
finally:
# this block is always executed
# regardless of exception generation.
print('This is always executed')
输出:
5
This is always executed
例 3:
# Python program to demonstrate finally
# Exception is not handled
try:
k = 5//0 # exception raised
print(k)
finally:
# this block is always executed
# regardless of exception generation.
print('This is always executed')
输出:
This is always executed
运行时错误–
*Unhandled Exception*
k=5//0 #No exception raised
ZeroDivisionError: integer division or modulo by zero
说明: 在上面的代码中，异常是由整数除法或以零为模生成的，没有处理。执行最后块后，异常再次出现。这表明无论是否处理异常，最终都执行块。
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