How to find files with a string

[anton.gridushko at gmail.com]

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

Process finished with exit code 1

Could you help me to solve this thread?