Python utils

Python utils#

Reraise#

Reraise an exception with an additional message.

Usage as contextmanager:

with epy.maybe_reraise(f'Error for {x}: '):
  fn(x)

Usage using try/except:

try:
  fn(x)
except Exception as e:
  epy.reraise(e, prefix=f'Error for {x}: ')

Benefit: Contrary to raise ... from ... and raise Exception().with_traceback(tb), this function will:

  • Keep the original exception type, attributes,…

  • Avoid multi-nested During handling of the above exception, another exception occurred. Only the single original stacktrace is displayed.

This result in cleaner and more compact error messages.

Text utils#

  • epy.pprint: Pretty print a value, supports dataclasses.

  • epy.pretty_repr: Returns a pretty repr() of the given object, supports dataclasses.

  • epy.reverse_fstring: Parse string to match a f-string pattern

    epy.reverse_fstring(
    '/home/{user}/projects/{project}',
    '/home/conchylicultor/projects/menhir'
) == {
    'user': 'conchylicultor',
    'project': 'menhir',
}

  • epy.diff_str: Pretty diff between 2 objects.

  • epy.dedent: Like textwrap.dedent but also strip() the content.

Itertool utils#

  • epy.zip_dict: Iterate over items of dictionaries grouped by their keys.

    d0 = {'a': 1, 'b': 2}
d1 = {'a': 10, 'b': 20}

for k, (v0, v1) in epy.zip_dict(d0, d1):
  ...

  • epy.groupby: Similar to itertools.groupby but return result as a dict()

    assert epy.groupby(['ddd', 'c', 'aa', 'aa', 'bbb'], key=len) == {
    3: ['ddd', 'bbb'],
    1: ['c'],
    2: ['aa', 'aa'],
}

  • epy.splitby: Split the iterable into 2 lists (false, true), based on the predicate.

    small, big = epy.splitby([100, 4, 4, 1, 200], lambda x: x > 10)
assert small == [4, 4, 1]
assert big == [100, 200]

Class utils#

  • epy.ContextManager: Allows to define contextmanager class using yield-syntax.

    Example:

    class A(epy.ContextManager):

  def __contextmanager__(self) -> Iterable[A]:
    yield self


with A() as a:
  pass

  • epy.frozen: Class decorator to make it immutable (except in __init__).

    @epy.frozen
class A:

  def __init__(self):
    self.x = 123

a = A()
a.x = 456  # AttributeError

    Supports inheritance, child classes should explicitly be marked as @epy.frozen if they mutate additional attributes in __init__.

  • epy.wraps_cls: Equivalent of @functools.wraps, but applied to classes.

  • epy.is_namedtuple: Returns True if the value is instance of NamedTuple.

  • epy.issubclass: Like issubclass, but do not raise error if value is not type.

Thread-utils#

With edc (dataclass utils), you can create a stack object which is both thread-safe and contextvars-safe:

from etils import edc

_stack = edc.ContextStack[int]()

@contextlib.contextmanager
def my_thread_safe_contextmanager():
  _stack.append(1)
  try:
    yield
  finally:
    _stack.pop()

Miscellaneous#

  • epy.StrEnum: Like enum.StrEnum, but is case insensitive.

  • epy.lazy_imports: Context Manager to lazy load modules (for optional dependencies or speed-up import time).

  • epy.ExitStack: Like contextlib.ExitStack but supports setting the contextmanagers at init time.

Environment utils#

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