Merge pull request #279 from realpython/sort-dict

How to Sort a Python Dictionary

Author: bzaczynski

sort-python-dictionary/README.md

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+# How to Sort a Python Dictionary
+
+Corresponding code for ["How to Sort a Python Dictionary"](https://realpython.com/sort-python-dictionary/)

sort-python-dictionary/compare_lambda_vs_getter.py

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+from timeit import timeit
+
+dict_to_order = {
+    1: "requests",
+    2: "pip",
+    3: "jinja",
+    4: "setuptools",
+    5: "pandas",
+    6: "numpy",
+    7: "black",
+    8: "pillow",
+    9: "pyparsing",
+    10: "boto3",
+    11: "botocore",
+    12: "urllib3",
+    13: "s3transfer",
+    14: "six",
+    15: "python-dateutil",
+    16: "pyyaml",
+    17: "idna",
+    18: "certifi",
+    19: "typing-extensions",
+    20: "charset-normalizer",
+    21: "awscli",
+    22: "wheel",
+    23: "rsa",
+}
+
+sorted_with_lambda = "sorted(dict_to_order.items(), key=lambda item: item[1])"
+sorted_with_itemgetter = "sorted(dict_to_order.items(), key=itemgetter(1))"
+
+sorted_with_lambda_time = timeit(stmt=sorted_with_lambda, globals=globals())
+sorted_with_itemgetter_time = timeit(
+    stmt=sorted_with_itemgetter,
+    setup="from operator import itemgetter",
+    globals=globals(),
+)
+
+print(
+    f"""\
+{sorted_with_lambda_time=:.2f} seconds
+{sorted_with_itemgetter_time=:.2f} seconds
+itemgetter is {(
+    sorted_with_lambda_time / sorted_with_itemgetter_time
+):.2f} times faster"""
+)

sort-python-dictionary/compare_lookup_dict_vs_list.py

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+from timeit import timeit
+
+lookups = [15, 18, 19, 16, 6, 12, 5, 3, 9, 20, 2, 10, 13, 17, 4, 14, 11, 7, 8]
+
+list_setup = """
+from samples import list_of_dictionaries
+
+def get_key_from_list(key):
+    for item in list_of_dictionaries:
+        if item["id"] == key:
+            return item
+"""
+
+dict_setup = "from samples import dictionary_of_dictionaries"
+
+lookup_list = """
+for key in lookups:
+    get_key_from_list(key)
+"""
+
+lookup_dict = """
+for key in lookups:
+    dictionary_of_dictionaries[key]
+"""
+
+lookup_list_time = timeit(
+    stmt=lookup_list, setup=list_setup, globals=globals()
+)
+lookup_dict_time = timeit(
+    stmt=lookup_dict, setup=dict_setup, globals=globals()
+)
+
+print(
+    f"""\
+{lookup_list_time=:.2f} seconds
+{lookup_dict_time=:.2f} seconds
+dict is {(lookup_list_time / lookup_dict_time):.2f} times faster"""
+)

sort-python-dictionary/compare_sorting_dict_vs_list.py

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+from timeit import timeit
+
+sorting_list = "sorted(list_of_dictionaries, key=lambda item:item['age'])"
+sorting_dict = """
+dict(
+    sorted(
+        dictionary_of_dictionaries.items(), key=lambda item: item[1]['age']
+    )
+)
+"""
+
+sorting_list_time = timeit(
+    stmt=sorting_list,
+    setup="from samples import list_of_dictionaries",
+    globals=globals(),
+)
+sorting_dict_time = timeit(
+    stmt=sorting_dict,
+    setup="from samples import dictionary_of_dictionaries",
+    globals=globals(),
+)
+
+print(
+    f"""\
+{sorting_list_time=:.2f} seconds
+{sorting_dict_time=:.2f} seconds
+list is {(sorting_dict_time/sorting_list_time):.2f} times faster"""
+)

sort-python-dictionary/nested_sort.py

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+data = {
+    193: {"name": "John", "age": 30, "skills": {"python": 8, "js": 7}},
+    209: {"name": "Bill", "age": 15, "skills": {"python": 6}},
+    746: {"name": "Jane", "age": 58, "skills": {"js": 2, "python": 5}},
+    109: {"name": "Jill", "age": 83, "skills": {"java": 10}},
+    984: {"name": "Jack", "age": 28, "skills": {"c": 8, "assembly": 7}},
+    765: {"name": "Penelope", "age": 76, "skills": {"python": 8, "go": 5}},
+    598: {"name": "Sylvia", "age": 62, "skills": {"bash": 8, "java": 7}},
+    483: {"name": "Anna", "age": 24, "skills": {"js": 10}},
+    277: {"name": "Beatriz", "age": 26, "skills": {"python": 2, "js": 4}},
+}
+
+
+def get_python(item):
+    skills = item[1]["skills"]
+    if "python" in skills:
+        return skills["python"]
+    else:
+        # Return value that is equivalent to having no Python skill
+        return 0
+
+
+print(sorted(data.items(), key=get_python, reverse=True))
+
+# Doing the same thing with lambda function and conditional expression
+print(
+    sorted(
+        data.items(),
+        key=lambda item: item[1]["skills"]["python"]
+        if "python" in item[1]["skills"]
+        else 0,
+        reverse=True,
+    )
+)

sort-python-dictionary/samples.py

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+dictionary_of_dictionaries = {
+    1: {"first_name": "Dorthea", "last_name": "Emmanuele", "age": 29},
+    2: {"first_name": "Evelina", "last_name": "Ferras", "age": 91},
+    3: {"first_name": "Frederica", "last_name": "Livesay", "age": 99},
+    4: {"first_name": "Murray", "last_name": "Linning", "age": 36},
+    5: {"first_name": "Annette", "last_name": "Garioch", "age": 93},
+    6: {"first_name": "Rozamond", "last_name": "Todd", "age": 36},
+    7: {"first_name": "Tiffi", "last_name": "Varian", "age": 28},
+    8: {"first_name": "Noland", "last_name": "Cowterd", "age": 51},
+    9: {"first_name": "Dyana", "last_name": "Fallows", "age": 100},
+    10: {"first_name": "Diahann", "last_name": "Cutchey", "age": 44},
+    11: {"first_name": "Georgianne", "last_name": "Steinor", "age": 32},
+    12: {"first_name": "Sabina", "last_name": "Lourens", "age": 31},
+    13: {"first_name": "Lynde", "last_name": "Colbeck", "age": 35},
+    14: {"first_name": "Abdul", "last_name": "Crisall", "age": 84},
+    15: {"first_name": "Quintus", "last_name": "Brando", "age": 95},
+    16: {"first_name": "Rowena", "last_name": "Geraud", "age": 21},
+    17: {"first_name": "Maurice", "last_name": "MacAindreis", "age": 83},
+    18: {"first_name": "Pall", "last_name": "O'Cullinane", "age": 79},
+    19: {"first_name": "Kermie", "last_name": "Willshere", "age": 20},
+    20: {"first_name": "Holli", "last_name": "Tattoo", "age": 88},
+}
+
+list_of_dictionaries = [
+    {"id": 1, "first_name": "Dorthea", "last_name": "Emmanuele", "age": 29},
+    {"id": 2, "first_name": "Evelina", "last_name": "Ferras", "age": 91},
+    {"id": 3, "first_name": "Frederica", "last_name": "Livesay", "age": 99},
+    {"id": 4, "first_name": "Murray", "last_name": "Linning", "age": 36},
+    {"id": 5, "first_name": "Annette", "last_name": "Garioch", "age": 93},
+    {"id": 6, "first_name": "Rozamond", "last_name": "Todd", "age": 36},
+    {"id": 7, "first_name": "Tiffi", "last_name": "Varian", "age": 28},
+    {"id": 8, "first_name": "Noland", "last_name": "Cowterd", "age": 51},
+    {"id": 9, "first_name": "Dyana", "last_name": "Fallows", "age": 100},
+    {"id": 10, "first_name": "Diahann", "last_name": "Cutchey", "age": 44},
+    {"id": 11, "first_name": "Georgianne", "last_name": "Steinor", "age": 32},
+    {"id": 12, "first_name": "Sabina", "last_name": "Lourens", "age": 31},
+    {"id": 13, "first_name": "Lynde", "last_name": "Colbeck", "age": 35},
+    {"id": 14, "first_name": "Abdul", "last_name": "Crisall", "age": 84},
+    {"id": 15, "first_name": "Quintus", "last_name": "Brando", "age": 95},
+    {"id": 16, "first_name": "Rowena", "last_name": "Geraud", "age": 21},
+    {"id": 17, "first_name": "Maurice", "last_name": "MacAindreis", "age": 83},
+    {"id": 18, "first_name": "Pall", "last_name": "O'Cullinane", "age": 79},
+    {"id": 19, "first_name": "Kermie", "last_name": "Willshere", "age": 20},
+    {"id": 20, "first_name": "Holli", "last_name": "Tattoo", "age": 88},
+]

sort-python-dictionary/sorting_a_dictionary.py

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+# Reviewing the sorted() function by sorting a list
+numbers = [5, 3, 4, 3, 6, 7, 3, 2, 3, 4, 1]
+sorted(numbers)
+words = ["aa", "ab", "ac", "ba", "cb", "ca"]
+sorted(words)
+
+
+def select_second_character(word):  # Sort key
+    return word[1]
+
+
+sorted(words, key=select_second_character)
+
+# Feeding dictionary directly into sorted() function
+people = {3: "Jim", 2: "Jack", 4: "Jane", 1: "Jill"}
+sorted(people)  # Returns list of sorted keys (values gone)
+
+# Getting dictionary views
+people = {3: "Jim", 2: "Jack", 4: "Jane", 1: "Jill"}
+people.items()
+
+people = {3: "Jim", 2: "Jack", 4: "Jane", 1: "Jill"}
+view = people.items()
+people[2] = "Elvis"
+print(view)  # View has been updated
+
+# Feeding dictionary view directly into sorted() function
+people = {3: "Jim", 2: "Jack", 4: "Jane", 1: "Jill"}
+sorted(people.items())  # Sorts by key
+
+# Using a sort key when sorting dictionary views
+people = {3: "Jim", 2: "Jack", 4: "Jane", 1: "Jill"}
+
+
+def value_getter(item):  # Sort key
+    return item[1]
+
+
+sorted(people.items(), key=value_getter)
+sorted(people.items(), key=lambda item: item[1])  # Sort key as lambda function
+
+
+# Building a dictionary from the list returned from the sorted() function
+sorted_people = sorted(people.items(), key=lambda item: item[1])
+
+sorted_people_dict = {}  # Using a for loop
+for key, value in sorted_people:
+    sorted_people_dict[key] = value
+
+sorted_people = sorted(people.items(), key=lambda item: item[1])
+sorted_people_dict = dict(sorted_people)  # dictionary constructor
+
+sorted_people_dict = {  # dictionary comprehension that swaps keys and values
+    value: key
+    for key, value in sorted(people.items(), key=lambda item: item[1])
+}

sort-python-dictionary/using_itemgetter.py

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+from operator import itemgetter
+
+item = ("name", "Guido")
+
+getter = itemgetter(0)
+getter(item)  # Returns "name"
+
+getter = itemgetter(1)
+getter(item)  # Returns "Guido"
+
+
+fruit_inventory = [("banana", 5), ("orange", 15), ("apple", 3), ("kiwi", 0)]
+
+# Sort by key
+sorted(fruit_inventory, key=itemgetter(0))
+
+# Sort by value
+sorted(fruit_inventory, key=itemgetter(1))
+
+# Raises IndexError
+# sorted(fruit_inventory, key=itemgetter(2))
+
+
+people = {3: "Jim", 2: "Jack", 4: "Jane", 1: "Jill"}
+
+sorted(people.items(), key=itemgetter(1))  # Sort by value
+
+
+scores = {
+    "Jack": 14,
+    "Jill": 14,
+    "John": 15,
+    "Jane": 15,
+    "Jim": 14,
+    "Jess": 14,
+}
+
+# Sorts by value, but keeps names in alphabetical order
+print(sorted(scores.items(), key=itemgetter(1, 0)))