Locate

This library provides three callables:

• this_dir() returns the directory of the current Python file, or when using from an interactive session, it returns the current working directory.
• append_sys_path(relative_path) allows importing from a location relative to the running Python file by resolving relative_path relative to this_dir() and appending it to sys.path (e.g. relative_path="../foo/bar"). This also works as a context manager to allow temporary effect (e.g. with append_sys_path("foo"): ...).
• prepend_sys_path(relative_path) is the same as append_sys_path, but prepending sys.path in order to be the first import location for Python to search rather than the last.

Safety

The *_sys_path destructors (when exiting the with block) are safe from any side effect your package imports may have on sys.path. It's not a naive implementation such as removing the first/last element or removing the element by value; it employs a string subclass with an additional id property to keep tags of sys.path insertions. It is, therefore, completely safe and allows for any further nesting of with *_sys_path within the import tree.

Examples

Input

import locate
from pathlib import Path

this_dir = locate.this_dir()

print(f"This file is located in: {this_dir}")
print()

# Create files to demonstrate importing from a directory
foo = Path(locate.this_dir(), "foo")
foo.mkdir(exist_ok=True)

Path(foo, "bar1.py").write_text("print('Importing bar1')")
Path(foo, "bar2.py").write_text("print('Importing bar2')")
Path(foo, "bar3.py").write_text("print('Importing bar3')")
Path(foo, "bar4.py").write_text("print('Importing bar4')")

# Changing sys.path temporarily
with locate.prepend_sys_path("foo"):
    print(f"I can temporarily import from: {Path(this_dir, 'foo')}")
    import bar1

    print()

print(f"I can no longer import from: {Path(this_dir, 'foo')}")
try:
    import bar2
except ImportError:
    print("Cannot import bar2")
print()

# Changing sys.path permanently
locate.prepend_sys_path("foo")
print(f"I can now always import from: {Path(this_dir, 'foo')}")
import bar3
import bar4

print()

Output

This file is located in: C:\Users\simon

I can temporarily import from: C:\Users\simon\foo
Importing bar1

I can no longer import from: C:\Users\simon\foo
Cannot import bar2

I can now always import from: C:\Users\simon\foo
Importing bar3
Importing bar4

Motivation

This package is for people who frequently use the directory of their scripts for storing files and custom modules and do not want their pipeline to break from an interactive shell. This is based on how Julia thinks about the immediate directory through its @__DIR__ macro.

locate.this_dir() is defined as:

• When running a .py file, this is the file's base directory.
• When running an .ipyn notebook, this is the current working directory. This is the desired/expected result since Jupyter sets the working directory as the .ipynb base directory by default.
• When running in a REPL, this is also the current working directory. This is similar to Julia's @__DIR__ macro.

Other considerations

For a good discussion on retrieving the current Python path, see https://stackoverflow.com/questions/3718657