#!/usr/bin/env python3
+# © Copyright 2021-2022, Scott Gasch
+
+"""Helper functions for dealing with dictionaries."""
+
from itertools import islice
-from typing import Any, Callable, Dict, Iterator, Tuple
+from typing import Any, Callable, Dict, Iterator, List, Tuple
def init_or_inc(
key: Any,
*,
init_value: Any = 1,
- inc_function: Callable[..., Any] = lambda x: x + 1
+ inc_function: Callable[..., Any] = lambda x: x + 1,
) -> bool:
"""
Initialize a dict value (if it doesn't exist) or increments it (using the
False
>>> d
{'test': 2, 'ing': 1}
+
"""
if key in d.keys():
d[key] = inc_function(d[key])
"""
items = d.items()
for x in range(0, len(d), size):
- yield {key: value for (key, value) in islice(items, x, x + size)}
+ yield dict(islice(items, x, x + size))
-def coalesce_by_creating_list(key, v1, v2):
+def coalesce_by_creating_list(_, new_value, old_value):
+ """Helper for use with :meth:`coalesce` that creates a list on
+ collision."""
from list_utils import flatten
- return flatten([v1, v2])
+ return flatten([new_value, old_value])
+
+
+def coalesce_by_creating_set(key, new_value, old_value):
+ """Helper for use with :meth:`coalesce` that creates a set on
+ collision."""
+ return set(coalesce_by_creating_list(key, new_value, old_value))
-def coalesce_by_creating_set(key, v1, v2):
- return set(coalesce_by_creating_list(key, v1, v2))
+def coalesce_last_write_wins(_, new_value, discarded_old_value):
+ """Helper for use with :meth:`coalsce` that klobbers the old
+ with the new one on collision."""
+ return new_value
-def raise_on_duplicated_keys(key, v1, v2):
+
+def coalesce_first_write_wins(_, discarded_new_value, old_value):
+ """Helper for use with :meth:`coalsce` that preserves the old
+ value and discards the new one on collision."""
+ return old_value
+
+
+def raise_on_duplicated_keys(key, new_value, old_value):
+ """Helper for use with :meth:`coalesce` that raises an exception
+ when a collision is detected.
+ """
raise Exception(f'Key {key} is duplicated in more than one input dict.')
def coalesce(
- inputs: Iterator[Dict[Any, Any]],
- *,
- aggregation_function: Callable[[Any, Any], Any] = coalesce_by_creating_list
+ inputs: Iterator[Dict[Any, Any]],
+ *,
+ aggregation_function: Callable[[Any, Any, Any], Any] = coalesce_by_creating_list,
) -> Dict[Any, Any]:
- """Merge N dicts into one dict containing the union of all keys/values in
- the input dicts. When keys collide, apply the aggregation_function which,
- by default, creates a list of values. See also coalesce_by_creating_set or
- provide a user defined aggregation_function.
+ """Merge N dicts into one dict containing the union of all keys /
+ values in the input dicts. When keys collide, apply the
+ aggregation_function which, by default, creates a list of values.
+ See also several other alternative functions for coalescing values:
+
+ * :meth:`coalesce_by_creating_set`
+ * :meth:`coalesce_first_write_wins`
+ * :meth:`coalesce_last_write_wins`
+ * :meth:`raise_on_duplicated_keys`
+ * or provive your own collision resolution code.
>>> a = {'a': 1, 'b': 2}
>>> b = {'b': 1, 'c': 2, 'd': 3}
>>> c = {'c': 1, 'd': 2}
>>> coalesce([a, b, c])
{'a': 1, 'b': [1, 2], 'c': [1, 2], 'd': [2, 3]}
+
+ >>> coalesce([a, b, c], aggregation_function=coalesce_last_write_wins)
+ {'a': 1, 'b': 1, 'c': 1, 'd': 2}
+
+ >>> coalesce([a, b, c], aggregation_function=raise_on_duplicated_keys)
+ Traceback (most recent call last):
+ ...
+ Exception: Key b is duplicated in more than one input dict.
+
"""
out: Dict[Any, Any] = {}
for d in inputs:
def item_with_max_value(d: Dict[Any, Any]) -> Tuple[Any, Any]:
- """Returns the key and value with the max value in a dict.
+ """Returns the key and value of the item with the max value in a dict.
>>> d = {'a': 1, 'b': 2, 'c': 3}
>>> item_with_max_value(d)
Traceback (most recent call last):
...
ValueError: max() arg is an empty sequence
+
"""
return max(d.items(), key=lambda _: _[1])
def item_with_min_value(d: Dict[Any, Any]) -> Tuple[Any, Any]:
- """Returns the key and value with the min value in a dict.
+ """Returns the key and value of the item with the min value in a dict.
>>> d = {'a': 1, 'b': 2, 'c': 3}
>>> item_with_min_value(d)
('a', 1)
+
"""
return min(d.items(), key=lambda _: _[1])
>>> d = {'a': 1, 'b': 2, 'c': 3}
>>> key_with_max_value(d)
'c'
+
"""
return item_with_max_value(d)[0]
>>> d = {'a': 1, 'b': 2, 'c': 3}
>>> key_with_min_value(d)
'a'
+
"""
return item_with_min_value(d)[0]
>>> d = {'a': 1, 'b': 2, 'c': 3}
>>> max_value(d)
3
+
"""
return item_with_max_value(d)[1]
>>> d = {'a': 1, 'b': 2, 'c': 3}
>>> min_value(d)
1
+
"""
return item_with_min_value(d)[1]
>>> d = {'a': 3, 'b': 2, 'c': 1}
>>> max_key(d)
'c'
+
"""
return max(d.keys())
>>> d = {'a': 3, 'b': 2, 'c': 1}
>>> min_key(d)
'a'
+
"""
return min(d.keys())
+def parallel_lists_to_dict(keys: List[Any], values: List[Any]) -> Dict[Any, Any]:
+ """Given two parallel lists (keys and values), create and return
+ a dict.
+
+ >>> k = ['name', 'phone', 'address', 'zip']
+ >>> v = ['scott', '555-1212', '123 main st.', '12345']
+ >>> parallel_lists_to_dict(k, v)
+ {'name': 'scott', 'phone': '555-1212', 'address': '123 main st.', 'zip': '12345'}
+
+ """
+ if len(keys) != len(values):
+ raise Exception("Parallel keys and values lists must have the same length")
+ return dict(zip(keys, values))
+
+
+def dict_to_key_value_lists(d: Dict[Any, Any]) -> Tuple[List[Any], List[Any]]:
+ """
+ >>> d = {'name': 'scott', 'phone': '555-1212', 'address': '123 main st.', 'zip': '12345'}
+ >>> (k, v) = dict_to_key_value_lists(d)
+ >>> k
+ ['name', 'phone', 'address', 'zip']
+ >>> v
+ ['scott', '555-1212', '123 main st.', '12345']
+
+ """
+ r: Tuple[List[Any], List[Any]] = ([], [])
+ for (k, v) in d.items():
+ r[0].append(k)
+ r[1].append(v)
+ return r
+
+
if __name__ == '__main__':
import doctest
+
doctest.testmod()
projects / python_utils.git / blobdiff