3.7.文件操作

file = open(file, mode='r', encoding=None)

# 只读模式打开文本文件
file = open('data.txt', 'r', encoding='utf-8')

# 写入模式打开文件
file = open('output.txt', 'w', encoding='utf-8')

# 二进制模式打开文件
file = open('image.jpg', 'rb')

# 读取整个文件内容
with open('example.txt', 'r', encoding='utf-8') as file:
    content = file.read()
    print(content)

# 使用 readline() 逐行读取
with open('example.txt', 'r', encoding='utf-8') as file:
    line = file.readline()
    while line:
        print(line.strip())
        line = file.readline()

# 使用 readlines() 读取所有行
with open('example.txt', 'r', encoding='utf-8') as file:
    lines = file.readlines()
    for line in lines:
        print(line.strip())

# 直接遍历文件对象（推荐方式）
with open('example.txt', 'r', encoding='utf-8') as file:
    for line in file:
        print(line.strip())

# 读取前100个字符
with open('example.txt', 'r', encoding='utf-8') as file:
    chunk = file.read(100)
    print(chunk)

# 分块读取大文件
with open('large_file.txt', 'r', encoding='utf-8') as file:
    while True:
        chunk = file.read(1000)  # 每次读取1000个字符
        if not chunk:            # 读取结束
            break
        print(chunk)

# 读取二进制文件
with open('image.jpg', 'rb') as file:
    chunk = file.read(1024)  # 读取1024字节
    print(chunk)

# 覆盖写入模式
with open('output.txt', 'w', encoding='utf-8') as file:
    file.write("Hello, World!\n")
    file.write("This is a new line.\n")

# 追加写入模式
with open('output.txt', 'a', encoding='utf-8') as file:
    file.write("This line is appended.\n")

# 准备要写入的字符串列表
lines = ["Line 1\n", "Line 2\n", "Line 3\n"]

# 使用 writelines() 批量写入
with open('output.txt', 'w', encoding='utf-8') as file:
    file.writelines(lines)

# 或者使用循环写入
with open('output.txt', 'w', encoding='utf-8') as file:
    for line in lines:
        file.write(line)

# 使用 with 语句自动管理文件资源
with open('example.txt', 'r', encoding='utf-8') as file:
    content = file.read()
    print(content)
# 文件会自动关闭，无需手动调用 file.close()

# 传统方式（不推荐）
file = open('example.txt', 'r', encoding='utf-8')
try:
    content = file.read()
    print(content)
finally:
    file.close()  # 必须手动关闭

# with 语句（推荐）
with open('example.txt', 'r', encoding='utf-8') as file:
    content = file.read()
    print(content)
# 自动关闭，更简洁安全

with open('example.txt', 'r', encoding='utf-8') as file:
    print(f"初始位置: {file.tell()}")  # 0
    content = file.read(5)
    print(f"读取后位置: {file.tell()}")  # 5

with open('example.txt', 'rb') as file:
    # 移动到文件开头
    file.seek(0)
    print(f"位置: {file.tell()}")  # 0
    
    # 移动到第10个字节
    file.seek(10)
    print(f"位置: {file.tell()}")  # 10
    
    # 从当前位置向后移动5个字节
    file.seek(5, 1)
    print(f"位置: {file.tell()}")  # 15
    
    # 从文件末尾向前移动10个字节
    file.seek(-10, 2)
    print(f"位置: {file.tell()}")  # 文件大小-10

import os

# 检查文件是否存在
if os.path.exists('demo.txt'):
    print("文件存在")
else:
    print("文件不存在")

# 判断是文件还是目录
if os.path.isfile('demo.txt'):
    print("是文件")
if os.path.isdir('test_folder'):
    print("是目录")

# 获取文件大小
size = os.path.getsize('demo.txt')
print(f"文件大小: {size} 字节")

import os
from datetime import datetime

# 获取文件详细信息
info = os.stat('demo.txt')

print(f"文件大小: {info.st_size} 字节")
print(f"创建时间: {datetime.fromtimestamp(info.st_ctime)}")
print(f"最后访问: {datetime.fromtimestamp(info.st_atime)}")
print(f"最后修改: {datetime.fromtimestamp(info.st_mtime)}")
print(f"文件权限: {oct(info.st_mode)}")

# 1. 创建并写入文件
with open('demo.txt', 'w', encoding='utf-8') as file:
    file.write("这是第一行\n")
    file.write("这是第二行\n")
    file.write("这是第三行\n")

# 2. 读取并显示文件内容
print("文件内容:")
with open('demo.txt', 'r', encoding='utf-8') as file:
    for line_num, line in enumerate(file, 1):
        print(f"第{line_num}行: {line.strip()}")

# 3. 追加内容到文件
with open('demo.txt', 'a', encoding='utf-8') as file:
    file.write("这是追加的内容\n")

# 4. 显示追加后的内容
print("\n追加后的内容:")
with open('demo.txt', 'r', encoding='utf-8') as file:
    print(file.read())

文件内容:
第1行: 这是第一行
第2行: 这是第二行
第3行: 这是第三行

追加后的内容:
这是第一行
这是第二行
这是第三行
这是追加的内容

姓名,年龄,城市
张三,25,北京
李四,30,上海

import csv

# 写入 CSV 文件
with open('data.csv', 'w', newline='', encoding='utf-8') as file:
    writer = csv.writer(file)
    writer.writerow(['姓名', '年龄', '城市'])  # 写入表头
    writer.writerow(['张三', '25', '北京'])   # 写入数据
    writer.writerow(['李四', '30', '上海'])

# 读取 CSV 文件
with open('data.csv', 'r', newline='', encoding='utf-8') as file:
    reader = csv.reader(file)
    for row in reader:
        print(row)

import json

# 准备数据
data = {
    "name": "张三",
    "age": 25,
    "cities": ["北京", "上海", "广州"]
}

# 写入 JSON 文件
with open('data.json', 'w', encoding='utf-8') as file:
    json.dump(data, file, ensure_ascii=False, indent=4)

# 读取 JSON 文件
with open('data.json', 'r', encoding='utf-8') as file:
    loaded_data = json.load(file)
    print(loaded_data)

try:
    with open('nonexistent.txt', 'r', encoding='utf-8') as file:
        content = file.read()
        print(content)
except FileNotFoundError:
    print("文件不存在！")
except PermissionError:
    print("权限不足，无法访问文件！")
except IOError as e:
    print(f"文件操作错误: {e}")
except UnicodeDecodeError:
    print("文件编码错误！")
finally:
    print("文件操作完成")