How to find files with a string

[Peter Otten]

anton.gridushko at gmail.com wrote:

> Hello everyone!
> 
> I need to find a file, that contains a string TeNum
> 
> I try to
> 
> import os
> import sys
> def find_value(fname):
>     value = 0
>     with open(fname, encoding='cp866') as fn:
>         try:
>             for i in fn:
>                 if 'TeNam' in i:
>                     print(fname)
>         except IndexError:
>             pass

What's the purpose of that try...except?

>     return {fname}
> def main():
>     dirname = ('H:\\1\\3')
>     os.chdir(dirname)
>     res = {}

For historical reasons {} is the literal for an empty dict; you probably 
want a set:

      res = set()

>     for i in os.listdir(dirname):
>         res.update(find_value(i))
>     print('Filename is: ')
> if __name__ == "__main__":
>     main()
> 
> But there are mistakes like
> C:\Users\Anton\AppData\Local\Programs\Python\Python36-32\python.exe
> "C:/Users/Anton/PycharmProjects/Работа с файловой системой/Перебор файлов
> из папки.py" Traceback (most recent call last):
>   File "C:/Users/Anton/PycharmProjects/Работа с файловой системой/Перебор
>   файлов из папки.py", line 21, in <module>
>     main()
>   File "C:/Users/Anton/PycharmProjects/Работа с файловой системой/Перебор
>   файлов из папки.py", line 18, in main
>     res.update(find_value(i))
> ValueError: dictionary update sequence element #0 has length 35; 2 is
> required

You get the error because the dict.update() methods expects pairs:

>>> d = {}
>>> d.update({(1, 2)})
>>> d
{1: 2}

A string of length 2 will be taken as a pair,

>>> d.update({"xy"})
>>> d
{1: 2, 'x': 'y'}

but a string of any other length will not:

>>> d.update({"xyz"})
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: dictionary update sequence element #0 has length 3; 2 is 
required

> 
> Process finished with exit code 1
> 
> Could you help me to solve this thread?