code.py

# Copyright 2019 Google LLC
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     https://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

from typing import (Callable, Iterable, List, Optional, Tuple, TypeVar)
import itertools


def empty(content: str) -> bool:
    """Return True if this file has no Python statements, False otherwise.

    Args:
        content (str): A string containing Python code (or a lack thereof).
    """
    return not any([i.lstrip() and not i.lstrip().startswith('#')
                    for i in content.split('\n')])


T = TypeVar('T')


def partition(predicate: Callable[[T], bool],
              iterator: Iterable[T]) -> Tuple[List[T], List[T]]:
    """Partitions an iterable into two lists based on a predicate

    Args:
        predicate (Callable[[T], bool]) : A callable predicate on a single argument
                                          of whatever type is in iterator.
        iterator (Iterable(T)):           An iterable on any type.


    Returns:
        Tuple[List[T], List[T]]: The contents of iterator partitioned into two lists.
                                 The first list contains the "true" elements
                                 and the second contains the "false" elements.
    """
    results: Tuple[List[T], List[T]] = ([], [])

    for i in iterator:
        results[int(predicate(i))].append(i)

    # Returns trueList, falseList
    return results[1], results[0]


def nth(iterable: Iterable[T], n: int, default: Optional[T] = None) -> Optional[T]:
    """Return the nth element of an iterable or a default value.

    Args
        iterable (Iterable(T)): An iterable on any type.
        n (int):                The 'index' of the lement to retrieve.
        default (Optional(T)):  An optional default elemnt if the iterable has
                                 fewer than n elements.
    """
    return next(itertools.islice(iterable, n, None), default)