Open files in directory in for loop Python

Question

I'm a beginner programmer.

In my Py script, I need to create a CSV file with information from multiple files within a sub directory. When I ran my code, I got the error: FileNotFoundError: [Errno 2] No such file or directory: '1'. I printed the contents of the directory and found that the directory doesn't read the file's actual name but replaces it with a number or character.

Question: Is that typical of directories? Because in research, it seemed like other people are able to use

for file in directory:
    open(file, "r")

correctly. Am I missing something?

My code:

sub_dir = datetime + "-dir"
os.mkdir(sub_dir)

with open("csv.txt", "a") as csv, open("data.txt") as data:
    csv.write("Title" + "\r")
    for x in data:
        csv.write("," + x)
    csv.write("\r" + "Data")                
    for file in sub_dir:
        csv.write(file)
        csv.write(", " + "Word1")
        csv.write(", " + "Word2")
        csv.write(", " + "Word3")
        csv.write(", " + "Word4")
        csv.write("\r")
        f = open(file, "r")
        lines = f.readlines()
        for line in lines:
            line.replace("word5=", ", ")
            line.replace("word6=", ", ")
            line.replace("word7=", ", ")
            csv.write(line)

Question: How can I change my code so that file is the actual file name?

Answer 1

The problem is this line:

for file in sub_dir:

If you print(file) each time through the loop, it should be obvious what's wrong: subdir is a string, so you're just iterating over the characters of that string one by one.

What you probably wanted here is:

for file in os.listdir(sub_dir):

As the docs explain, listdir:

Return a list containing the names of the entries in the directory given by path. The list is in arbitrary order. It does not include the special entries '.' and '..' even if they are present in the directory.

Answer 2

sub_dir isn't a directory; it's the name of a directory.

for file in sub_dir:

iterates over the characters in the name.