无法捕获 IndexError 并打印语句，也循环回输入

Question

我可以循环 ValueError，但只有 ValueError 会打印语句

并且 IndexError 将停止代码，我想继续向用户询问 'line number'。

def file_content(file_name):
    user_file = open(file_name, 'r')
    content = user_file.readlines()
    user_file.close()
    return content

def main():
    file_name = input('Enter the name of the file: ')

    try:
        content = file_content(file_name)
    

    except IOError:
        print ('File can not be fount. Program will exit.')
        exit()

    while True:
    
        try:
            line_number = input('Enter a line number: ')
            line_number = int(line_number)
            break
        
        
        except IndexError:
            print ('That is not a valid line number. Try again.')
        
        except ValueError:
            print ('You need to enter an integer for the line number. Try again.')
        
    
        
    
    print ('The line you requested:')
    print (content[line_number-1])

    
main()

这就是我运行代码

时发生的情况

Enter the name of the file: datas.txt
Enter a line number: w
You need to enter an integer for the line number. Try again.
Enter a line number: 99
The line you requested:
Traceback (most recent call last):
File "/Users/yenvivian/Desktop/Python HW/hw04.py", line 40, in <module>
main()
File "/Users/yenvivian/Desktop/Python HW/hw04.py", line 37, in main
print (content[line_number-1])
IndexError: list index out of range

谢谢

Answer 1

要捕获异常，引发异常的代码必须在try:

的内部

try:
    line_number = input('Enter a line number: ')
    line_number = int(line_number)

    print ('The line you requested:')
    print (content[line_number-1])  # Inside the try

    break
        
        
except IndexError:
    print ('That is not a valid line number. Try again.')
    
except ValueError:
    print ('You need to enter an integer for the line number. Try again.')

无法捕获 IndexError 并打印语句，也循环回输入

Couldn't catch the IndexError and print the statement, also loop back to the input

python

try-except

index-error