python3中出现“”_io.TextIOWrapper“”对象不可订阅错误“”

Question

我正在做一个小程序，为了把我的一天都吃光！我正在读取一个文件，并将每行存储在一个变量中，如下所示：

cline = f[num_lines]

我不知道为什么这一行会出现这个错误，下面是我的完整代码：

import os
number_lines = 1
print('Enter the filepath to the file you want to read.')
fpath = input('Enter: ')
print('okay')
with open(fpath, 'r') as f:
    for line in f:
        cline = f[num_lines]
        originalline = number_lines
        number_lines += 1
        length = len(line)
        if cline[0] == 'e' and cline[1] == 'c' and cline[2] == 'h' and cline[3] == 'o' and cline[4] == '':
          echoing = cline[5:length]
          print(echoing)
        else:
          print('N# Does not recognize that command! In line: ' + str(originalline))

提前谢谢你，我不知道为什么这不起作用。

Answer 1

这条线

cline = f[num_lines] 

不起作用，因为f是一个TextIOWrapper (或文件)对象，并且它没有提供允许[index]操作的__getitem__方法。此外，未定义num_lines。当前行的内容已经保存在变量line中，因此不需要定义cline。

这个版本的代码可以工作(我将最后的字符串测试修改为line[4] == " "，因为line[4] == ""永远不可能为真)。

number_lines = 1
print("Enter the filepath to the file you want to read.")
fpath = input("Enter: ")
print("okay")
with open(fpath, "r") as f:
    for line in f:
        originalline = number_lines
        number_lines += 1
        length = len(line)
        if (
            line[0] == "e"
            and line[1] == "c"
            and line[2] == "h"
            and line[3] == "o"
            and line[4] == " "
        ):
            echoing = line[5:length]
            print(echoing)
        else:
            print("N# Does not recognize that command! In line: " + str(originalline))

如果需要，可以使用enumerate内置函数跟踪行号，使用str.startswith测试每行的开头，从而减少代码量。

print("Enter the filepath to the file you want to read.")
fpath = input("Enter: ")
print("okay")
with open(fpath, "r") as f:
    for number_lines, line in enumerate(f, start=1):
        length = len(line)
        if line.startswith("echo "):
            echoing = line[5:length]
            print(echoing)
        else:
            print("N# Does not recognize that command! In line: " + str(number_lines))