Python 一旦提供了有效的文件名，如何退出for循环，并为正确输入提供3次机会

我试图写一个for循环，让用户尝试3次提供正确的文件名。做这件事的最佳方式或最佳实践是什么

for n in [1,2,3]:
    try:
        user_inp = input('Please provide the filename: ')  # Prompt user for file name
    # Need help here..
    # If the filename isn't found, python will give the following error: FileNotFoundError: [Errno 2] No such file or directory: 
    # If that happens, I need it to print the except statement and try again 
    # However, if the filename is correct or "FileIsFound" I need it to exit the loop--using ' break ' ?         
    except:
          print('Invalid file name, try again please')
    # Would be great if we could add a counter here like: print('You have', n, 'tries remaining') 
    continue

file_open = open(user_inp) # open file --load in memory 

for line in file_open:  # remove /n at the end of each line
line = line.rstrip()  # print statements add /n = newlines and text docs usually have /n in them
# this for loop will remove/strip the /n at the end of each line

read_file = file_open.read()  # reads entire file 
                              # NOTE: if you are dealing with large files, you may want to consider using a conditional statement to find what you are searching, extracting, etc instead of reading the entire file


print(read_file.upper())  # Prints file contents in upper case 

我想知道如何用try-and-except语句来实现这一点。谢谢大家!

---

干杯

操作系统模块

使用

os

模块中的

isfile（）

方法检查文件是否存在

演示：

中断关键字

使用

break

关键字从任意迭代器循环中出来，即

for

，

while

演示

---

从用户处获取文件名并验证文件名的代码

import os

file_path = ""
for n in [1,2,3]:
    user_inp = raw_input('Please provide the filename: ')
    if os.path.isfile(user_inp):
        file_path = user_inp
        break 
    print('Invalid file name, try again please')


if file_path:
    # Write ypur code.
    print "Processing file Name:", file_path
else:
    print "User not enters correct file name."

输出：

$ python test1.py
Please provide the filename: /home/Desktop/1.txt
Invalid file name, try again please
Please provide the filename: /home/Desktop/2.txt                
Invalid file name, try again please
Please provide the filename: /home/Desktop/3.txt            
Invalid file name, try again please
User not enters correct file name.

$ python test1.py
Please provide the filename: /home/Desktop/2.txt
Invalid file name, try again please
Please provide the filename: /home/vivek/Desktop/file3.csv
Processing file Name: /home/vivek/Desktop/file3.csv

---

注意：

对Python2.x使用

raw\u input（）

对Python3.x使用

input（）

import os

file_path = ""
for n in [1,2,3]:
    user_inp = raw_input('Please provide the filename: ')
    if os.path.isfile(user_inp):
        file_path = user_inp
        break 
    print('Invalid file name, try again please')


if file_path:
    # Write ypur code.
    print "Processing file Name:", file_path
else:
    print "User not enters correct file name."

$ python test1.py
Please provide the filename: /home/Desktop/1.txt
Invalid file name, try again please
Please provide the filename: /home/Desktop/2.txt                
Invalid file name, try again please
Please provide the filename: /home/Desktop/3.txt            
Invalid file name, try again please
User not enters correct file name.

$ python test1.py
Please provide the filename: /home/Desktop/2.txt
Invalid file name, try again please
Please provide the filename: /home/vivek/Desktop/file3.csv
Processing file Name: /home/vivek/Desktop/file3.csv