Python报错不要慌,这三个关键词帮你解决问题!

陈python 2020-11-17 21:02:50
Python 报错 不要 三个 这三个


写代码必然会出现错误,而错误处理可以针对这些错误提前做好准备。通常出现错误时,脚本会停止运行,而有了错误处理,脚本就可以继续运行。为此,我们需要了解下面三个关键词:

  • try:这是要运行的代码块,可能会产生错误。
  • except:如果在try块中出现错误,将执行这段代码。
  • finally:不管出现什么错误,都要执行这段代码。

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现在,我们定义一个函数“summation”,将两个数字相加。该函数运行正常。

>>> defsummation(num1,num2):
print(num1+num2)>>>summation(2,3)
5

接下来,我们让用户输入其中一个数字,并运行该函数。

>>> num1 = 2
>>> num2 = input("Enter number: ")
Enter number: 3>>> summation(num1,num2)>>> print("Thisline will not be printed because of the error")
---------------------------------------------------------------------------
TypeError Traceback (most recent call last)
<ipython-input-6-2cc0289b921e> in <module>
----> 1 summation(num1,num2)
2 print("This line will notbe printed because of the error")
<ipython-input-1-970d26ae8592> in summation(num1, num2)
1 def summation(num1,num2):
----> 2 print(num1+num2)
TypeError: unsupported operand type(s) for +: int and str

  

“TypeError”错误出现了,因为我们试图将数字和字符串相加。请注意,错误出现后,后面的代码便不再执行。所以我们要用到上面提到的关键词,确保即使出错,脚本依旧运行。

>> try:
summed = 2 + 3
except:
print("Summation is not ofthe same type")Summation is not of the same type

可以看到,try块出现错误,except块的代码开始运行,并打印语句。接下来加入“else”块,来应对没有错误出现的情况。

>>> try:
summed = 2 + 3
except:
print("Summation is not ofthe same type")
else:
print("There was no errorand result is: ",summed)There was no error and result is: 5

接下来我们用另外一个例子理解。这个例子中,在except块我们还标明了错误类型。如果没有标明错误类型,出现一切异常都会执行except块。

>>> try:
f = open( test , w )
f.write("This is a testfile")
except TypeError:
print("There is a typeerror")
except OSError:
print("There is an OSerror")
finally:
print("This will print evenif no error")This will print even if no error

现在,故意创造一个错误,看看except块是否与finally块共同工作吧!

>>> try:
f = open( test , r )
f.write("This is a testfile")
except TypeError:
print("There is a typeerror")
except OSError:
print("There is an OSerror")
finally:
print("This will print evenif no error")There is an OS error
This will print even if no error

 

版权声明
本文为[陈python]所创,转载请带上原文链接,感谢
https://www.cnblogs.com/4186c/p/13996372.html

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