Python Modules & Imports: Master Third‑Party Packages in 5 Minutes

Core Goal

Master module import methods, install third‑party packages, avoid mirror errors, and unlock automation or web‑scraping capabilities within five minutes.

What is a module?

A module is pre‑written code packaged for reuse. Built‑in modules come with Python, while third‑party modules must be installed.

Three import styles

# Import the whole module
import random
print(random.randint(1, 10))

# Import specific functions
from random import randint, choice
print(randint(1, 5))
print(choice(["apple", "banana", "orange"]))

# Import with alias
import math as m
print(m.sqrt(36))

Installing third‑party modules

Use pip install package_name. When the default mirrors (Aliyun, Douban) fail, switch to Tsinghua or USTC mirrors:

pip install -i https://pypi.tuna.tsinghua.edu.cn/simple requests
# or
pip install -i https://pypi.mirrors.ustc.edu.cn/simple requests

Comprehensive example

Generate random scores, classify them, and print results:

import random

def get_grade(score):
    if score >= 90:
        return "优秀"
    elif score >= 80:
        return "良好"
    elif score >= 60:
        return "及格"
    else:
        return "不及格"

def generate_random_scores(n):
    scores = []
    for i in range(n):
        score = random.randint(60, 100)
        scores.append(score)
    for score in scores:
        grade = get_grade(score)
        print(f"成绩：{score}，等级：{grade}")

generate_random_scores(5)

Common pitfalls and solutions

ModuleNotFoundError – install the module using a reliable mirror.

Mirror parsing errors – switch to Tsinghua or USTC mirror URLs.

Forgot to prefix function with module name – use either module.function() or from module import function.

Misspelled module name – verify exact spelling.

Post‑lesson task

# 1. Compute 10² and 2³ with math
import math
print(math.pow(10, 2))
print(math.pow(2, 3))

# 2. Install requests via Tsinghua mirror
# pip install -i https://pypi.tuna.tsinghua.edu.cn/simple requests

# 3. Generate three random numbers between 1 and 20
import random
nums = [random.randint(1, 20) for _ in range(3)]
print(nums)

Key takeaways

Modules are ready‑made toolkits; built‑in modules are ready to use, third‑party modules require installation from reliable mirrors.

Three import patterns: whole module, specific functions, and alias.

When errors occur, first check installation, mirror source, and spelling.