Recursive function to return a dictionary in Python

Question

I have the tree of above. I need to search in a recursive way the directories and files from the tree and return them as a dictionary in the following form -> key: directories/name of file and value: first line of file

eg: key:1/2/5/test5    value:first line of test 5

So far, i created the next code:

def search(root):
    items = os.listdir(root)
    
    for element in items:
        if os.path.isfile(element):
        
            with open (element) as file:
                one_line=file.readline()
                print(one_line)

        elif os.path.isdir(element):
            search(os.path.join(root,element))

The problem is that my code only searches the directories. Please make me understand where i'm wrong and how to solve it. Massive appreciation for any help, thank you!

What do you mean my code only searches the directories? Why don't you use a dictionary to save file information before printing one_line? — Ice
– Ice, Commented Jan 8, 2022 at 21:20

s.dallapalma · Accepted Answer · 2022-01-08 22:04:26Z

1

Your code is almost correct. It has to be adjusted a little, though. More specifically,

element is a file or directory name (not path). If it is a subdirectory or file in a subdirectory the value of if os.path.isfile(element) and elif os.path.isdir(element) will be always False. Hence, replace them with if os.path.isfile(os.path.join(root, element)) and elif os.path.isdir(os.path.join(root, element)) respectively.
Similarly, with open(element) should be replaced by with open(os.path.join(root,element)).
When reading the file's first line, you have to store the path and that line in a dictionary.
That dictionary has to be updated when calling the recursive function in elif os.path.isdir(element).

See below for the complete snippet:

import os

def search(root):

    my_dict = {}   # this is the final dictionary to be populated

    for element in os.listdir(root):
        
        if os.path.isfile(os.path.join(root, element)):
            try: 
                with open(os.path.join(root, element)) as file:
                    my_dict[os.path.join(root, element)] = file.readline() # populate the dictionary
            except UnicodeDecodeError: 
                # This exception handling has been put here to ignore decode errors (some files cannot be read)
                pass

        elif os.path.isdir(os.path.join(root, element)):
            my_dict.update(search(os.path.join(root,element)))  # update the current dictionary with the one resulting from the recursive call

    return my_dict

print(search('.'))

It prints a dictionary like below:

{
 "path/file.csv": "name,surname,grade",
 "path/to/file1.txt": "this is the first line of file 1",
 "path/to/file2.py": "import os"
}

For the sake of readability, os.path.join(root, element) can be stored in a variable, then:

import os

def search(root):

    my_dict = {}   # this is the final dictionary to be populated

    for element in os.listdir(root):
        path = os.path.join(root, element)

        if os.path.isfile(path):
            with open(path) as file:
                my_dict[path] = file.readline()

        elif os.path.isdir(path):
            my_dict.update(search(path))

    return my_dict

print(search('.'))

edited Jan 8, 2022 at 22:04

answered Jan 8, 2022 at 21:57

s.dallapalma

1,3231 gold badge13 silver badges39 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

Andrei Over a year ago

You have an upvote from me. The problem was..as you said... with the os.path.join(root, element) for os.path.isdir and os.path.isfile. Can you tell me why it is needed to make the join for every isfile and isdir? I want to learn and write that is my logbook. Please make me understand or send me a link with the information.

s.dallapalma Over a year ago

In your tree, you start the search at directory where only "1" is present. Therefore, through the recursive calls, element will be "1", then "2", then "5", then "test5" and so on so forth. Obviously, they are NOT recognized as files and directory since they are not in the current directory. Using the join, element will be "./1", then "1/2" (second recursive call), then "1/2/5" (at the third recursive call), and finally "1/2/5/test5". That is, you can access subdirectories and files

s.dallapalma Over a year ago

Please, if that solves your problem mark the answer as "accepted"

sinankanidagli · Accepted Answer · 2022-01-08 21:46:41Z

1

You can use os.walk

The following function will not include empty folders.

def get_tree(startpath):
    tree = {}
    for root, dirs, files in os.walk(startpath):
        for file in files:
            path = root+"/"+file
            with open(path,'r') as f:
                first_line =  f.readline()
            tree[path] = first_line
    return tree

The output will be like this:

{
    file_path : first_line_of_the_file,
    file_path2 : first_line_of_the_file2,
    ...
}

edited Jan 8, 2022 at 21:46

answered Jan 8, 2022 at 21:37

sinankanidagli

113 bronze badges

1 Comment

Andrei Over a year ago

Thank you very much for your help!:) The idea of using os.walk() was my second option. I really wanted to create a recursive function to search directories, but if i won't find a solution, i will try to use os.walk().

Collectives™ on Stack Overflow

Recursive function to return a dictionary in Python

2 Answers 2

3 Comments

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

3 Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related