morecontext 0.1.0

Context managers for changing directory, setting attributes/envvars, etc.

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morecontext provides context managers for some common minor operations: specifically, changing the current working directory, an object’s attribute, a dict field, or an environment variable and then setting it back afterwards. Sure, it’s easy enough to implement these on your own, but why bother doing that over & over again when you can let this package do it for you once?

Type annotated! Fully tested!

Installation

morecontext requires Python 3.6 or higher. Just use pip for Python 3 (You have pip, right?) to install morecontext:

python3 -m pip install morecontext

Examples

>>> import os
>>> import morecontext
>>> os.getcwd()
'/some/dir'
>>> with morecontext.dirchanged('/some/other/dir'):
...     # Now we're in /some/other/dir
...     os.getcwd()
...
'/some/other/dir'
>>> # Out of the `with`, back to /some/dir
>>> os.getcwd()
'/some/dir'

>>> d = {"foo": 42}
>>> with morecontext.itemset(d, "foo", "bar"):
...     # d["foo"] == "bar" in here
...     d["foo"]
...     # If we change d["foo"] in here, it'll still be set back to 42 on exit
...     d["foo"] = 3.14
...
'bar'
>>> # Out of the `with`, it's back to 42
>>> d["foo"]
42

API

All of the context managers in morecontext are defined with contextlib.contextmanager, so they can be used as function decorators as well. All context managers return None on entry, so there’s no point in writing “with dirchanged(path) as foo:”; just do “with dirchanged(path):”.

These functions are not thread-safe.

dirchanged(dirpath: os.PathLike) -> ContextManager[None]

dirchanged(dirpath) returns a context manager. On entry, it stores the current working directory path and then changes the current directory to dirpath. On exit, it changes the current directory back to the stored path.

attrset(obj: Any, name: str, value: Any) -> ContextManager[None]

attrset(obj, name, value) returns a context manager. On entry, it stores the current value of the attribute of obj with name name, and then it sets that attribute to value. On exit, it sets the attribute back to the stored value.

If the given attribute is unset on entry, the context manager will unset it on exit.

attrdel(obj: Any, name: str) -> ContextManager[None]

attrdel(obj, name) returns a context manager. On entry, it stores the current value of the attribute of obj with name name, and then it unsets that attribute. On exit, it sets the attribute back to the stored value.

If the given attribute is unset on entry, the context manager will unset it on exit.

itemset(d: MutableMapping[K,V], key: K, value: V) -> ContextManager[None]

itemset(d, key, value) returns a context manager. On entry, it stores the current value of d[key], and then it sets that field to value. On exit, it sets the field back to the stored value.

If the given field is unset on entry, the context manager will unset it on exit.

itemdel(d: MutableMapping[K, Any], key: K) -> ContextManager[None]

itemdel(d, key) returns a context manager. On entry, it stores the current value of d[key], and then it unsets that field. On exit, it sets the field back to the stored value.

If the given field is unset on entry, the context manager will unset it on exit.

envset(name: str, value: str) -> ContextManager[None]

envset(name, value) returns a context manager. On entry, it stores the current value of the environment variable name, and then it sets that environment variable to value. On exit, it sets the environment variable back to the stored value.

If the given environment variable is unset on entry, the context manager will unset it on exit.

envdel(name: str) -> ContextManager[None]

envdel(name) returns a context manager. On entry, it stores the current value of the environment variable name, and then it unsets that environment variable. On exit, it sets the environment variable back to the stored value.

If the given environment variable is unset on entry, the context manager will unset it on exit.