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I had to write a custom function to load a yaml file from the current working directory. The function itself works and my intention was to write it in a pure fashion but my senior colleague told me that the way I wrote this function is utterly bad and I have to rewrite it.

Which commandment in Python did I violate? Can anyone tell me what I did wrong here and how a "professional" solution would look like?

from typing import Dict
import yaml
from yaml import SafeLoader
from pathlib import Path
import os


def read_yaml_from_cwd(file: str) -> Dict:

    """[reads a yaml file from current working directory]
    Parameters
    ----------
    file : str
        [.yaml or .yml file]
    Returns
    -------
    Dict
        [Dictionary]
    """
    path = os.path.join(Path.cwd().resolve(), file)
    if os.path.isfile(path):
        with open(path) as f:
            content = yaml.load(f, Loader=SafeLoader)
            return content
    else:
        return None

content = read_yaml_from_cwd("test.yaml")
print(content)
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1 Answer 1

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Which commandment did you violate? Using os.path and pathlib in the same breath! pathlib is an object-oriented replacement to os.path.

    path = os.path.join(Path.cwd().resolve(), file)
    if os.path.isfile(path):
        with open(path) as f:

could be written as:

    path = Path.cwd().joinpath(file)
    if path.is_file():
        with path.open() as f:

or since you're starting at the current directory, simply:

    path = Path(file)
    if path.is_file():
        with path.open() as f:
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3
  • \$\begingroup\$ I am using ruamel yaml in my own project, so I might be missremembering the details. I thought one could simply do content = yaml.load(path, Loader=SafeLoader) directly on the path without having to explicitly open it? \$\endgroup\$ Dec 2, 2021 at 19:00
  • \$\begingroup\$ @N3buchadnezzar That may be true; I haven't used yaml at all. My answer focused on the mashup between os.path and pathlib, stopping just before the yaml.load(...) line for that very reason. \$\endgroup\$
    – AJNeufeld
    Dec 2, 2021 at 19:05
  • \$\begingroup\$ thank you, very helpful! \$\endgroup\$
    – DSGym
    Dec 2, 2021 at 19:06

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