Basic Output and String Handling

The print() function outputs data to the console. Special characters like quotes can be escaped with a backslash:

print('Let\'s go!')
print("He said, \"Hello!\"")

Use \t for tabs and triple quotes for multi-line strings:

print('''Line one
Line two''')

Variables and Naming

Python 3 supports Unicode identifiers, allowing varialbe names in Chinese or other languages:

姓名 = "张三"
print(姓名)

String Manipulation

Common string methods include case conversion and whitespace trimming:

text = "  Hello World  "
print(text.strip().title())  # "Hello World"

F-strings enable embedded expressions:

name = "Alice"
greeting = f"Hi, {name.upper()}!"
print(greeting)  # "Hi, ALICE!"

Numeric Operations

The math module provides advanced functions:

import math
print(math.sqrt(16))   # 4.0
print(math.log(100, 10))  # 2.0

Data Types

Key types include:

• str: Text sequences (e.g., "abc")
• bool: True or False
• NoneType: Represents absence of value (None)

Type inspection and length:

value = 42.0
print(type(value))  # <class 'float'>
print(len("Python"))  # 6

List Operations

Create and modify lists:

items = ["apple", "banana"]
items.append("cherry")
items.insert(1, "blueberry")
items.remove("banana")

Sorting and iteration:

numbers = [3, 1, 4]
for num in sorted(numbers):
    print(num)

Dictionaries

Store key-value pairs with immutable keys:

inventory = {
    ("widget", "A"): 150,
    ("gadget", "B"): 89
}
print(inventory[("widget", "A")])  # 150

Iterate through entries:

for product, stock in inventory.items():
    if stock < 100:
        print(f"Low stock: {product}")

Control Flow

for loops iterate over known sequences; while loops continue until a conditoin fails:

count = 0
while count < 3:
    print(count)
    count += 1

Functions

Define reusable blocks of code:

def calculate_area(radius):
    return 3.14159 * radius ** 2

area = calculate_area(5)

Object-Oreinted Programming

Classes encapsulate data and behavior:

class Vehicle:
    def __init__(self, make, model):
        self.make = make
        self.model = model
    
    def describe(self):
        return f"{self.make} {self.model}"

car = Vehicle("Toyota", "Camry")
print(car.describe())

Inheritance extends functionality:

class ElectricCar(Vehicle):
    def __init__(self, make, model, battery_size):
        super().__init__(make, model)
        self.battery_size = battery_size

File Handling

Read and write files using pathlib:

from pathlib import Path

data_file = Path("data.txt")
content = data_file.read_text()
lines = content.splitlines()

output_file = Path("output.txt")
output_file.write_text("Processed data")

Error Handling

Manage exceptions gracefully:

try:
    number = int(input("Enter a number: "))
except ValueError:
    print("Invalid input")
else:
    print(f"Square: {number ** 2}")

Data Visualization

Install packages efficiently using mirrors:

pip install -i https://pypi.tuna.tsinghua.edu.cn/simple matplotlib

Process structured data formats:

import csv
import json

# Read CSV
with open("data.csv") as f:
    reader = csv.reader(f)
    headers = next(reader)

# Format JSON
data = {"key": "value"}
print(json.dumps(data, indent=2))