1
Python 3.x.x

1
hello.py

1
print("Hello, Python")

1
Hello, Python

1
>>>

1
1 + 2
2
"hello".upper()

1
user_name = "zgm"
2
order_count = 10
3
is_paid = False

1
a = "zgm"
2
x1 = 10
3
flag = False

1
age = 23
2
age = "二十三"

1
age = "23"
2
print(age + 1)

1
MAX_RETRY = 3
2
APP_NAME = "personal-blog-tool"

1
MAX_RETRY = 100

1
count = 10
2
price = 19.9
3
total = count * price
4
print(total)

1
print(10 + 3)  # 13
2
print(10 - 3)  # 7
3
print(10 * 3)  # 30
4
print(10 / 3)  # 3.333...
5
print(10 // 3) # 3，整除
6
print(10 % 3)  # 1，取余
7
print(2 ** 3)  # 8，幂

1
print(6 / 3)   # 2.0
2
print(6 // 3)  # 2

1
name = "zgm"
2
city = 'Nanjing'

1
message = """
2
第一行
3
第二行
4
第三行
5
"""

1
name = "zgm"
2

3
print(name.upper())      # ZGM
4
print(name.startswith("z"))
5
print(len(name))

1
first = "hello"
2
second = "python"
3
print(first + " " + second)

1
name = "zgm"
2
age = 23
3
print(f"{name} is {age} years old")

1
is_active = True
2
is_deleted = False

1
age = 20
2
print(age >= 18)  # True

1
user = None

1
if user is None:
2
    print("no user")

1
if user == None:
2
    print("no user")

1
names = ["Tom", "Jerry", "Alice"]

1
print(names[0])   # Tom
2
print(names[-1])  # Alice

1
names.append("Bob")

1
names.remove("Jerry")

1
for name in names:
2
    print(name)

1
for index, name in enumerate(names):
2
    print(index, name)

1
numbers = [1, 2, 3, 4, 5]
2

3
print(numbers[0:2])  # [1, 2]
4
print(numbers[:3])   # [1, 2, 3]
5
print(numbers[2:])   # [3, 4, 5]

1
a = [1, 2]
2
b = a
3
b.append(3)
4
print(a)  # [1, 2, 3]

1
b = a.copy()

1
point = (10, 20)

1
x = point[0]
2
y = point[1]

1
x, y = point

1
def get_position():
2
    return 10, 20
3

4

5
x, y = get_position()

1
user = {
2
    "id": 1,
3
    "name": "zgm",
4
    "age": 23,
5
}

1
print(user["name"])

1
nickname = user.get("nickname", "")

1
user["age"] = 24

1
user["email"] = "test@example.com"

1
for key, value in user.items():
2
    print(key, value)

1
tags = {"Python", "Go", "Python"}
2
print(tags)  # {'Python', 'Go'}

1
if "Python" in tags:
2
    print("has python")

1
a = {"Python", "Go", "PHP"}
2
b = {"Python", "JavaScript"}
3

4
print(a & b)  # 交集
5
print(a | b)  # 并集
6
print(a - b)  # 差集

1
age = 20
2

3
if age >= 18:
4
    print("adult")
5
else:
6
    print("child")

1
score = 85
2

3
if score >= 90:
4
    print("A")
5
elif score >= 80:
6
    print("B")
7
elif score >= 60:
8
    print("C")
9
else:
10
    print("D")

1
if score >= 60:
2
print("pass")

1
age = 20
2
label = "adult" if age >= 18 else "child"

1
names = ["Tom", "Jerry", "Alice"]
2

3
for name in names:
4
    print(name)

1
for i in range(5):
2
    print(i)

1
for i in range(1, 6):
2
    print(i)

1
for i in range(0, 10, 2):
2
    print(i)

1
count = 0
2

3
while count < 3:
4
    print(count)
5
    count += 1

1
while True:
2
    print("bad")

1
for number in [1, 2, 3, 4, 5]:
2
    if number == 3:
3
        break
4
    print(number)

1
for number in [1, 2, 3, 4, 5]:
2
    if number % 2 == 0:
3
        continue
4
    print(number)

1
status = "paid"
2

3
match status:
4
    case "pending":
5
        print("待支付")
6
    case "paid":
7
        print("已支付")
8
    case "cancelled":
9
        print("已取消")
10
    case _:
11
        print("未知状态")

1
def add(a, b):
2
    return a + b
3

4

5
result = add(1, 2)

1
def handle_user_order_payment_notify_report():
2
    ...

1
def connect(host, port=3306):
2
    print(host, port)
3

4

5
connect("localhost")
6
connect("localhost", 3307)

1
def add_item(item, items=[]):
2
    items.append(item)
3
    return items

1
def add_item(item, items=None):
2
    if items is None:
3
        items = []
4
    items.append(item)
5
    return items

1
def create_user(name, age, city):
2
    return {
3
        "name": name,
4
        "age": age,
5
        "city": city,
6
    }
7

8

9
user = create_user(name="zgm", age=23, city="Nanjing")

1
def total(*numbers):
2
    result = 0
3
    for number in numbers:
4
        result += number
5
    return result
6

7

8
print(total(1, 2, 3))

1
def print_profile(**profile):
2
    for key, value in profile.items():
3
        print(key, value)
4

5

6
print_profile(name="zgm", age=23)

1
name = "global"
2

3

4
def show():
5
    name = "local"
6
    print(name)
7

8

9
show()
10
print(name)

1
def add(a, b):
2
    return a + b

1
from math_utils import add
2

3
print(add(1, 2))

1
my_app/
2
  main.py
3
  user/
4
    __init__.py
5
    service.py

1
def get_user_name():
2
    return "zgm"

1
from user.service import get_user_name
2

3
print(get_user_name())

1
.venv/
2
__pycache__/
3
*.pyc

1
from pathlib import Path
2

3
path = Path("example.txt")
4
content = path.read_text(encoding="utf-8")
5

6
print(content)

1
from pathlib import Path
2

3
path = Path("output.txt")
4
path.write_text("Hello, Python", encoding="utf-8")

1
from pathlib import Path
2

3
path = Path("users.txt")
4

5
for line in path.read_text(encoding="utf-8").splitlines():
6
    print(line)

1
from pathlib import Path
2

3
path = Path("large.log")
4

5
with path.open("r", encoding="utf-8") as file:
6
    for line in file:
7
        print(line.rstrip())

1
import json
2
from pathlib import Path
3

4
path = Path("user.json")
5
data = json.loads(path.read_text(encoding="utf-8"))
6

7
print(data["name"])

1
import json
2
from pathlib import Path
3

4
user = {
5
    "id": 1,
6
    "name": "zgm",
7
    "skills": ["Python", "Go", "PHP"],
8
}
9

10
path = Path("user.json")
11
path.write_text(
12
    json.dumps(user, ensure_ascii=False, indent=2),
13
    encoding="utf-8",
14
)

1
import csv
2
from pathlib import Path
3

4
path = Path("users.csv")
5

6
with path.open("r", encoding="utf-8", newline="") as file:
7
    reader = csv.DictReader(file)
8
    for row in reader:
9
        print(row["name"], row["age"])

1
import csv
2
from pathlib import Path
3

4
rows = [
5
    {"name": "Tom", "age": 20},
6
    {"name": "Jerry", "age": 21},
7
]
8

9
path = Path("users.csv")
10

11
with path.open("w", encoding="utf-8", newline="") as file:
12
    writer = csv.DictWriter(file, fieldnames=["name", "age"])
13
    writer.writeheader()
14
    writer.writerows(rows)

1
try:
2
    number = int("abc")
3
except ValueError:
4
    print("不是合法数字")

1
try:
2
    number = int("abc")
3
except Exception:
4
    pass

1
from pathlib import Path
2

3
path = Path("missing.txt")
4

5
try:
6
    content = path.read_text(encoding="utf-8")
7
except FileNotFoundError:
8
    print(f"文件不存在：{path}")

1
try:
2
    print("do something")
3
finally:
4
    print("cleanup")

1
def divide(a, b):
2
    if b == 0:
3
        raise ValueError("b 不能为 0")
4
    return a / b

1
class User:
2
    def __init__(self, user_id, name):
3
        self.user_id = user_id
4
        self.name = name
5

6
    def display_name(self):
7
        return f"{self.user_id}-{self.name}"
8

9

10
user = User(1, "zgm")
11
print(user.display_name())

1
from dataclasses import dataclass
2

3

4
@dataclass
5
class User:
6
    user_id: int
7
    name: str
8
    age: int
9

10

11
user = User(user_id=1, name="zgm", age=23)
12
print(user.name)

1
class Animal:
2
    def speak(self):
3
        return "..."
4

5

6
class Dog(Animal):
7
    def speak(self):
8
        return "wang"

1
class EmailSender:
2
    def send(self, message):
3
        print(f"email: {message}")
4

5

6
class NotificationService:
7
    def __init__(self, sender):
8
        self.sender = sender
9

10
    def notify(self, message):
11
        self.sender.send(message)

1
from pathlib import Path
2

3
base_dir = Path("data")
4
file_path = base_dir / "users.json"
5

6
print(file_path.exists())

1
import os
2

3
print(os.getenv("APP_ENV", "local"))

1
from datetime import datetime
2

3
now = datetime.now()
4
print(now.strftime("%Y-%m-%d %H:%M:%S"))

1
import json
2

3
text = '{"name": "zgm"}'
4
data = json.loads(text)

1
import re
2

3
text = "phone: 13800138000"
4
match = re.search(r"\d{11}", text)
5

6
if match:
7
    print(match.group())

1
import argparse
2

3
parser = argparse.ArgumentParser()
4
parser.add_argument("--name", required=True)
5

6
args = parser.parse_args()
7
print(f"hello {args.name}")

1
import subprocess
2

3
result = subprocess.run(
4
    ["python", "--version"],
5
    capture_output=True,
6
    text=True,
7
    check=True,
8
)
9

10
print(result.stdout)

1
name: str = "zgm"
2
age: int = 23
3
is_active: bool = True

1
def add(a: int, b: int) -> int:
2
    return a + b

1
names: list[str] = ["Tom", "Jerry"]
2
scores: dict[str, int] = {"Tom": 90}
3
tags: set[str] = {"Python", "Go"}
4
point: tuple[int, int] = (10, 20)

1
def find_user_name(user_id: int) -> str | None:
2
    if user_id == 1:
3
        return "zgm"
4
    return None

1
name = find_user_name(2)
2

3
if name is None:
4
    print("user not found")
5
else:
6
    print(name.upper())

1
from typing import TypedDict
2

3

4
class UserDict(TypedDict):
5
    id: int
6
    name: str
7
    age: int
8

9

10
def display_user(user: UserDict) -> str:
11
    return f"{user['id']}-{user['name']}"

1
todo_app/
2
  main.py
3
  todo_store.py
4
  todo_service.py
5
  todos.json

1
[
2
  {
3
    "id": 1,
4
    "title": "学习 Python 变量",
5
    "done": false
6
  }
7
]

1
import json
2
from pathlib import Path
3

4

5
DATA_FILE = Path("todos.json")
6

7

8
def load_todos() -> list[dict]:
9
    if not DATA_FILE.exists():
10
        return []
11

12
    text = DATA_FILE.read_text(encoding="utf-8")
13

14
    if not text.strip():
15
        return []
16

17
    return json.loads(text)
18

19

20
def save_todos(todos: list[dict]) -> None:
21
    DATA_FILE.write_text(
22
        json.dumps(todos, ensure_ascii=False, indent=2),
23
        encoding="utf-8",
24
    )

1
from todo_store import load_todos, save_todos
2

3

4
def list_todos() -> list[dict]:
5
    return load_todos()
6

7

8
def add_todo(title: str) -> dict:
9
    todos = load_todos()
10

11
    next_id = 1
12
    if todos:
13
        next_id = max(todo["id"] for todo in todos) + 1
14

15
    todo = {
16
        "id": next_id,
17
        "title": title,
18
        "done": False,
19
    }
20

21
    todos.append(todo)
22
    save_todos(todos)
23

24
    return todo
25

26

27
def complete_todo(todo_id: int) -> bool:
28
    todos = load_todos()
29

30
    for todo in todos:
31
        if todo["id"] == todo_id:
32
            todo["done"] = True
33
            save_todos(todos)
34
            return True
35

36
    return False

1
import argparse
2

3
from todo_service import add_todo, complete_todo, list_todos
4

5

6
def handle_list() -> None:
7
    todos = list_todos()
8

9
    if not todos:
10
        print("暂无待办")
11
        return
12

13
    for todo in todos:
14
        mark = "✓" if todo["done"] else " "
15
        print(f"{todo['id']}. [{mark}] {todo['title']}")
16

17

18
def handle_add(title: str) -> None:
19
    todo = add_todo(title)
20
    print(f"已添加：{todo['id']} - {todo['title']}")
21

22

23
def handle_done(todo_id: int) -> None:
24
    ok = complete_todo(todo_id)
25

26
    if ok:
27
        print("已完成")
28
    else:
29
        print("待办不存在")
30

31

32
def main() -> None:
33
    parser = argparse.ArgumentParser()
34
    subparsers = parser.add_subparsers(dest="command")
35

36
    subparsers.add_parser("list")
37

38
    add_parser = subparsers.add_parser("add")
39
    add_parser.add_argument("title")
40

41
    done_parser = subparsers.add_parser("done")
42
    done_parser.add_argument("id", type=int)
43

44
    args = parser.parse_args()
45

46
    if args.command == "list":
47
        handle_list()
48
    elif args.command == "add":
49
        handle_add(args.title)
50
    elif args.command == "done":
51
        handle_done(args.id)
52
    else:
53
        parser.print_help()
54

55

56
if __name__ == "__main__":
57
    main()

1
main.py  2000 行

1
try:
2
    do_something()
3
except Exception:
4
    pass

1
data = get_data()
2
handle(data)

1
users = load_users()
2
send_welcome_messages(users)