Merge pull request #614 from realpython/python-dicts

Sample code for the article on dictionaries

Author: brendaweles

python-dicts/README.md

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+# Dictionaries in Python
+
+This folder provides the code examples for the Real Python tutorial [Dictionaries in Python](https://realpython.com/python-dicts/).

python-dicts/configs.py

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+config = {
+    "color": "green",
+    "width": 42,
+    "height": 100,
+    "font": "Courier",
+}
+
+# Access a value through its key
+print(config["color"])
+
+# Update a value
+config["font"] = "Helvetica"
+print(config)
+
+config = {
+    "color": "green",
+    "width": 42,
+    "height": 100,
+    "font": "Courier",
+}
+user_config = {
+    "path": "/home",
+    "color": "red",
+    "font": "Arial",
+    "position": (200, 100),
+}
+config.update(user_config)
+print(config)
+config.update([("width", 200), ("api_key", 1234)])
+print(config)
+config.update(color="yellow", script="__main__.py")
+print(config)
+
+default_config = {
+    "color": "green",
+    "width": 42,
+    "height": 100,
+    "font": "Courier",
+}
+user_config = {
+    "path": "/home",
+    "color": "red",
+    "font": "Arial",
+    "position": (200, 100),
+}
+config = default_config | user_config
+print(config)
+
+config = {
+    "color": "green",
+    "width": 42,
+    "height": 100,
+    "font": "Courier",
+}
+user_config = {
+    "path": "/home",
+    "color": "red",
+    "font": "Arial",
+    "position": (200, 100),
+}
+config |= user_config
+print(config)

python-dicts/counter.py

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+from collections import Counter
+
+print(Counter("mississippi"))

python-dicts/dict_zip.py

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+cities = ["Colorado", "Chicago", "Boston", "Minnesota", "Milwaukee", "Seattle"]
+teams = ["Rockies", "White Sox", "Red Sox", "Twins", "Brewers", "Mariners"]
+
+print(dict(zip(cities, teams)))

python-dicts/employees.py

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+from collections import defaultdict
+
+employees = [
+    ("Sales", "John"),
+    ("Sales", "Martin"),
+    ("Accounting", "Kate"),
+    ("Marketing", "Elizabeth"),
+    ("Marketing", "Linda"),
+]
+
+departments = defaultdict(list)
+for department, employee in employees:
+    departments[department].append(employee)
+
+print(departments)

python-dicts/equality.py

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+print([1, 2, 3] == [3, 2, 1])
+print({1: 1, 2: 2, 3: 3} == {3: 3, 2: 2, 1: 1})
+print([1, 2, 3] != [3, 2, 1])
+print({1: 1, 2: 2, 3: 3} != {3: 3, 2: 2, 1: 1})

python-dicts/from_keys.py

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+inventory = dict.fromkeys(["apple", "orange", "banana", "mango"], 0)
+print(inventory)

python-dicts/inventory.py

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+inventory = {"apple": 100, "orange": 80, "banana": 100}
+inventory.get("apple")
+
+print(inventory.get("mango"))
+
+print(inventory.get("mango", 0))
+
+print(inventory.values())
+
+print(inventory.keys())
+
+print(inventory.items())

python-dicts/iteration.py

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+students = {
+    "Alice": 89.5,
+    "Bob": 76.0,
+    "Charlie": 92.3,
+    "Diana": 84.7,
+    "Ethan": 88.9,
+    "Fiona": 95.6,
+    "George": 73.4,
+    "Hannah": 81.2,
+}
+for student in students:
+    print(student)
+
+for student in students.keys():
+    print(student)
+
+for student in students:
+    print(student, "->", students[student])
+
+MLB_teams = {
+    "Colorado": "Rockies",
+    "Chicago": "White Sox",
+    "Boston": "Red Sox",
+    "Minnesota": "Twins",
+    "Milwaukee": "Brewers",
+    "Seattle": "Mariners",
+}
+for team in MLB_teams.values():
+    print(team)
+
+for city, team in MLB_teams.items():
+    print(city, "->", team)

python-dicts/membership.py

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+import timeit
+
+MLB_teams = {
+    "Colorado": "Rockies",
+    "Chicago": "White Sox",
+    "Boston": "Red Sox",
+    "Minnesota": "Twins",
+    "Milwaukee": "Brewers",
+    "Seattle": "Mariners",
+}
+
+# Run timeit to compare the membership test
+time_in_dict = timeit.timeit(
+    '"Milwaukee" in MLB_teams', globals=globals(), number=1000000
+)
+time_in_keys = timeit.timeit(
+    '"Milwaukee" in MLB_teams.keys()', globals=globals(), number=1000000
+)
+time_not_in_dict = timeit.timeit(
+    '"Indianapolis" in MLB_teams', globals=globals(), number=1000000
+)
+time_not_in_keys = timeit.timeit(
+    '"Indianapolis" in MLB_teams.keys()', globals=globals(), number=1000000
+)
+
+print(
+    f"{time_in_dict     = } seconds",
+    f"{time_in_keys     = } seconds",
+    f"{time_not_in_dict = } seconds",
+    f"{time_not_in_keys = } seconds",
+    sep="\n",
+)