issue with counting lines of python file

Question

I am traversing a directory, and if python file is found, trying to find the number of lines of code in it. I am not really sure why I face the below issue.

for dirpath, dirnames, filenames in os.walk(APP_FOLDER):

    for file in filenames:
        if pathlib.Path(file).suffix == ".py":
            num_lines = len(open(file).readlines()) #causes issue
            print(
                f"Root:{dirpath}\n"
                f"file:{file}\n\n"
                f"lines: {num_lines}" //
            )

Érror:

Traceback (most recent call last):
  File "C:\Users\XXXX\PycharmProjects\pythonProject1\main.py", line 11, in <module>
    num_lines = len(open(file).readlines())
FileNotFoundError: [Errno 2] No such file or directory: 

If i remove that line, the code works as expected. There is a single line code within. Any guidance here?

Answer 1

file is the file's name, not its path, to get its full path, join the name with the directory path dirpath using os.path.join. Also, it is better to use a with statement when dealing with files since it automatically closes the file:

file_path = os.path.join(dirpath, file)

with open(file_path) as f:
    num_lines = len(f.readlines())