Python常见模块及其用法示例详解

# 文件名为hello.py
def func():
	print("hello world!")
func()

import hello

mypackage/
│── __init__.py
│── module1.py
│── module2.py
└── subpackage/
    │── __init__.py
    │── module3.py

from mypackage import module1,module2
from mypackage.subpackage import module3

print(time.ctime()) 
# 输出：“Tue Jul 22 13:15:07 2025”

struct_time = time.localtime()
print(struct_time.tm_year, struct_time.tm_mon,struct_time.tm_mday) 
# 输出：2025 7 22

struct_time = time.localtime()
formatted = time.strftime("%Y-%m-%d %H:%M:%S",struct_time)
# 输出 2025-07-22 13:33:09

parsed_time = time.strptime("2025-07-22", "%Y-%m-%d") 
print(parsed_time)
# 输出:
# time.struct_time(tm_year=2025, tm_mon=7, tm_mday=22, tm_hour=0, tm_min=0, tm_sec=0, tm_wday=1, tm_yday=203, tm_isdst=-1)

start = time.perf_counter()
time.sleep(2)
end = time.perf_counter()
print(f"执行耗时：{end - start:.4f}秒")
# 输出:
# 执行耗时：2.0003秒

start = int(time.time())
time.sleep(2)
end = int(time.time())
print(f"停顿{end - start:.2f}秒")

# 输出:
# 停顿2.00秒

timestamp = time.time()
ts_to_struct = time.localtime(timestamp)
print(ts_to_struct)

# 输出:
# time.struct_time(tm_year=2025, tm_mon=7, tm_mday=22, tm_hour=13, tm_min=50, tm_sec=49, tm_wday=1, tm_yday=203, tm_isdst=0)

struct_time = time.localtime()
struct_to_ts = time.mktime(struct_time)
print(struct_to_ts)

# 输出:
# 1753163493.0

import os
os.mkdir("1") # 创建单级目录 | 文件已存在会报错
os.makedirs("test/1", exist_ok=True) # 创建多级目录，exist_ok=True，当文件已存在时不报错

import os
os.rename("old.txt","new.txt") # 重命名
os.remove("test/1.txt") # 删除文件

import os
for entry in os.scandir("."): # . 遍历当前目录下的所有 文件 和 子目录 
	if entry.is_file():
		print("文件：",entry)
# 输出：
# 文件： <DirEntry '1.py'>

import os

path = "/home/user/documents/report.txt"

# 获取路径组成部分
dir_path = os.path.dirname(path)  # 目录路径: "/home/user/documents"
file_name = os.path.basename(path)  # 完整文件名: "report.txt"
file_root, file_ext = os.path.splitext(file_name)  # 分离主名和扩展名: ("report", ".txt")

# 完整路径拆分
head, tail = os.path.split(path)  # ("/home/user/documents", "report.txt")

full_path = os.path.join("dir","subdir","file.txt")

print(os.path.exists("1.txt"))  # 是否存在
print(os.path.isfile("1.txt"))  # 是否是文件
print(os.path.isdir("1.txt"))  # 是否是目录

# 输出答案（根据个人本地要查询的文件为主）
# True
# True
# False

 cwd = os.getcwd()

 cwd = os.chdir("/new/path")

home_dir = os.enciron.get("HOME","default") # 查找 HOME 值，没有则返回默认值 default
print(home_dir)

os.system("ls -l")

# 假设执行：python scripts.py arg1 arg2 --option=value
print(sys.argv) # ['script.py', 'arg1', 'arg2', '--option=value']
# 实际应用：处理命令行选项
if len()sys.argv) > 1:
	action = sys.argv[1] # arg1
	if action == "start":
		print("")
	elif action == "stop":
		print("")

with open('1.txt','w',encoding="utf-8-sig") as f:
	sys.stdout = f # 重定向标准输出到文件
	print("这条信息将写入文件")
	sys.stdout = sys._stdout__ # 恢复标准输出
# 会将print中的内容写进 1.txt文件内

print("请输入内容：")
user_input = sys.stdin.readline().strip()
print(f"您输入了：{user_input}")

# 输出：
"""
请输入内容：
1 2 3 
您输入了：1 2 3
"""

print(sys.version)
# 输出
"""
3.11.9 (tags/v3.11.9:de54cf5, Apr  2 2024, 10:12:12) [MSC v.1938 64 bit (AMD64)]
"""

print(sys.path) 

# 输出列表形式，包含Python查找模块的路径

print(sys.platform) # 'win32', 'linux', 'darwin' (macOS)
# 输出 
"""
win32
"""

if error_occurred:
	sys.exit(1) # 非0状态码表示异常退出

print("处理中...", end="")
sys.stdout.flush()
# 执行耗时操作...
print("完成！")

import json
data = {
	"name": "Alice",
	"age": 30,
	"hobbies": ["reading"],
	"is_student": False,
}
json_str = json.dumps(data, indent=2)
print(json_str)

# 输出：
"""
{
  "name": "Alice",
  "age": 30,
  "hobbies": [
    "reading",
    "hiking"
  ],
  "is_student": false
}
"""

restored_data = json.loads(json_str)
print(restored_data["name"]) # "Alice"

with open("data.json", "w") as f:
	json.dump(data, f, indent=4) # 控制为 4 缩进空格

with open("data.json") as f:
	loaded_data = json.load(f)

# 处理自定义对象
class User:
    def __init__(self, name, age):
        self.name = name
        self.age = age
        
# 自定义序列化方法
def user_encoder(obj):
    if isinstance(obj, User): # 判断 obj 是否是 User 的实例
        return {"name": obj.name, "age": obj.age}
    raise TypeError(f"Object of type {obj.__class__.__name__} is not JSON serializable")

user = User("Bob", 40)
user_json = json.dumps(user, default=user_encoder)  # {"name": "Bob", "age": 40}

# 自定义反序列化方法
def user_decoder(dct):
    if "name" in dct and "age" in dct:
        return User(dct["name"], dct["age"])
    return dct

restored_user = json.loads(user_json, object_hook=user_decoder)
print(restored_user.name)  # "Bob"
```