replace environment variables in Path object

Path_expand.py

import os
from pathlib import Path
import warnings

# Create a new method for Path objects called `expand`, which fully 
# expands the Path object with the given environment variables.

def _expand(self, *, strict=True):
    """
    Fully expand and resolve the Path with the given environment variables.
    
    Parameters
    ----------
    strict : bool
        If True, must use the operating system syntax to find environment variables.
        - On Linux/Mac, environment variables look like ``${NAME}`` or ``$NAME``
        - On Windows, environment variables look like ``%NAME%``
        If False, just look for the path part in the os.environ dict 
        (i.e., HOME without symbols)
    """
    full_path = Path()
    for i in self.parts:
        if not strict:
            if i in os.environ:
                i = os.getenv(i)
        if i.startswith('$') or i.startswith('%'):
            # This might be an environment variable
            envar = i
            for ch in '${}%':
                if ch in envar:
                    envar = envar.replace(ch,"")
            if envar not in os.environ:
                warnings.warn(f'🦨 Sorry, [{i}] is not an environment variable.')
            else:
                i = os.getenv(envar)
        
        # Note: When you append to a path with a root, that path overwrites
        # the old path.
        # Example: Path('this/dir/') / Path('/p/home/') ==> Path(/p/home/) 
        # and not Path(this/dir//p/home/)
        full_path = full_path / i
    # Resolve path for `~`, `~blaylock`, `..`, `//`, and `.` 
    full_path = full_path.expanduser().resolve()
    return full_path

# Add the method to the Path class
Path.expand = _expand


# Test the new method

Path('~/').expand()
# > Path('/home/blaylock')

Path('$HOME/software').expand()
# > Path('/home/blaylock/software')

Path('HOME').expand()
# > NOT WHAT YOU MIGHT EXPECT >> Path('/home/blaylock/HOME')

Path('HOME').expand(strict=False)
# > Path('/home/blaylock')

Actually, that method can more simply be done like this

from pathlib import Path
import os

def _expand(self):
    """
    Fully expand and resolve the Path with the given environment variables.
    """
    return Path(os.path.expandvars(self)).expanduser().resolve()

Path.expand = _expand