Merge pull request #614 from realpython/python-dicts

Sample code for the article on dictionaries

python-dicts/README.md

@@ -0,0 +1,3 @@
+# 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

@@ -0,0 +1,62 @@
+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

@@ -0,0 +1,3 @@
+from collections import Counter
+
+print(Counter("mississippi"))

python-dicts/dict_zip.py

@@ -0,0 +1,4 @@
+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

@@ -0,0 +1,15 @@
+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

@@ -0,0 +1,4 @@
+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

@@ -0,0 +1,2 @@
+inventory = dict.fromkeys(["apple", "orange", "banana", "mango"], 0)
+print(inventory)

python-dicts/inventory.py

@@ -0,0 +1,12 @@
+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

@@ -0,0 +1,32 @@
+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

@@ -0,0 +1,32 @@
+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",
+)

python-dicts/mlb_teams.py

@@ -0,0 +1,33 @@
+MLB_teams = {
+    "Colorado": "Rockies",
+    # "Chicago": "White Sox",
+    "Chicago": "Chicago Cubs",
+    "Boston": "Red Sox",
+    "Minnesota": "Twins",
+    "Milwaukee": "Brewers",
+    "Seattle": "Mariners",
+}
+print(MLB_teams)
+
+MLB_teams = dict(
+    [
+        ("Colorado", "Rockies"),
+        ("Chicago", "White Sox"),
+        ("Boston", "Red Sox"),
+        ("Minnesota", "Twins"),
+        ("Milwaukee", "Brewers"),
+        ("Seattle", "Mariners"),
+    ]
+)
+print(MLB_teams)
+
+
+print("Milwaukee" in MLB_teams)
+print("Indianapolis" in MLB_teams)
+print("Indianapolis" not in MLB_teams)
+print("Milwaukee" in MLB_teams.keys())
+print("Indianapolis" in MLB_teams.keys())
+print("Indianapolis" not in MLB_teams.keys())
+
+print(("Boston", "Red Sox") in MLB_teams.items())
+print(("Boston", "Red Sox") not in MLB_teams.items())

python-dicts/number.py

@@ -0,0 +1,6 @@
+class Number:
+    def __init__(self, value):
+        self.value = value
+
+
+print(Number(42).__dict__)

python-dicts/person.py

@@ -0,0 +1,21 @@
+person = {
+    "first_name": "John",
+    "last_name": "Doe",
+    "age": 35,
+    "spouse": "Jane",
+    "children": ["Ralph", "Betty", "Bob"],
+    "pets": {"dog": "Frieda", "cat": "Sox"},
+}
+
+print(person["children"][0])
+print(person["children"][2])
+print(person["pets"]["dog"])
+
+person = {}
+person["first_name"] = "John"
+person["last_name"] = "Doe"
+person["age"] = 35
+person["spouse"] = "Jane"
+person["children"] = ["Ralph", "Betty", "Bob"]
+person["pets"] = {"dog": "Frieda", "cat": "Sox"}
+print(person)

python-dicts/sorted_dict.py

@@ -0,0 +1,35 @@
+class SortableDict(dict):
+    def sort_by_keys(self, reverse=False):
+        sorted_items = sorted(
+            self.items(), key=lambda item: item[0], reverse=reverse
+        )
+        self.clear()
+        self.update(sorted_items)
+
+    def sort_by_values(self, reverse=False):
+        sorted_items = sorted(
+            self.items(), key=lambda item: item[1], reverse=reverse
+        )
+        self.clear()
+        self.update(sorted_items)
+
+
+students = SortableDict(
+    {
+        "Alice": 89.5,
+        "Bob": 76.0,
+        "Charlie": 92.3,
+        "Diana": 84.7,
+        "Ethan": 88.9,
+        "Fiona": 95.6,
+        "George": 73.4,
+        "Hannah": 81.2,
+    }
+)
+
+print(id(students))
+students.sort_by_keys()
+print(students)
+students.sort_by_values(reverse=True)
+print(students)
+print(id(students))

python-dicts/squares.py

@@ -0,0 +1,10 @@
+squares = {}
+
+for integer in range(1, 10):
+    squares[integer] = integer**2
+
+print(squares)
+
+squares = {integer: integer**2 for integer in range(1, 10)}
+
+print(squares)

python-dicts/students.py

@@ -0,0 +1,12 @@
+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,
+}
+print(dict(sorted(students.items(), key=lambda item: item[1])))
+print(dict(sorted(students.items(), key=lambda item: item[1], reverse=True)))

python-dicts/values.py

@@ -0,0 +1,14 @@
+class Point:
+    def __init__(self, x, y):
+        self.x = x
+        self.y = y
+
+
+print(
+    {
+        "colors": ["red", "green", "blue"],
+        "plugins": {"py_code", "dev_sugar", "fasting_py"},
+        "timeout": 3,
+        "position": Point(42, 21),
+    }
+)