Why Does My Recursive Python Function Return None When Trying to Find a Path?

Returning a Path Recursively in Python

In Python, you have encountered an issue when attempting to return a path from a recursive function. Instead, you obtain None in the result.

The provided code seeks to traverse a dictionary representing a file system structure, searching for a file specified by rqfile. The path to that file should be returned if found.

The root cause of the issue is that while recursing through the dictionary, the function attempts to return None in the else branch when it encounters a non-dictionary value. This prematurely terminates the function, resulting in None being returned.

To rectify this, you need to consistently return the result of the recursive call:

for filename in dictionary.keys():
    path = prefix + [filename]
    if not isinstance(dictionary[filename], dict):          
        if rqfile in str(os.path.join(*path)):
            return str(os.path.join(*path))
    else:
        # Remove unnecessary else block
        return get_path(directory[filename], rqfile, path)

This code guarantees that the function returns the path if it's found or the result of the recursive call if the current path is not the one you're looking for. Alternatively, you can also handle the edge case where rqfile is not present in the current path:

for filename in dictionary.keys():
    path = prefix + [filename]
    if not isinstance(dictionary[filename], dict):          
        if rqfile in str(os.path.join(*path)):
            return str(os.path.join(*path))
        else:
            return None
    return get_path(directory[filename], rqfile, path)

By implementing either of these solutions, your function will correctly return the path to the requested file or None if it's not found.

The above is the detailed content of Why Does My Recursive Python Function Return None When Trying to Find a Path?. For more information, please follow other related articles on the PHP Chinese website!