跟着AI学Python 第7课：文件读写

# 第7课：文件读写 —— 让数据"活"起来

# 1.写入文件（w模式：覆盖写入）
file = open("test.txt", "w", encoding="utf-8")
file.write("第一行：Hello Python!\n")
file.write("第二行：文件读写真有趣\n")
file.close()          # 写完必须关闭，否则内容可能丢失
print("写入完成！")


print()


# 2.读取文件（r模式：只读）
file = open("test.txt", "r", encoding="utf-8")
content = file.read()       # 一次性读取全部内容
print(content)
file.close()


print()


# 3.逐行读取
file = open("test.txt", "r", encoding="utf-8")
line1 = file.readline()     # 读一行
line2 = file.readline()     # 再读一行
print(f"第一行：{line1}", end="")   # end=""因为原文本已有换行
print(f"第二行：{line2}", end="")
file.close()


print()
print()


# 4.读取所有行成列表
file = open("test.txt", "r", encoding="utf-8")
lines = file.readlines()    # 返回列表，每行一个元素
print(lines)                # ['第一行：Hello Python!\n', '第二行：文件读写真有趣\n']
for line in lines:
    print(f"→ {line}", end="")
file.close()


print()
print()


# 5.追加写入（a模式：在末尾追加，不覆盖）
file = open("test.txt", "a", encoding="utf-8")
file.write("第三行：追加的新内容\n")
file.close()

# 验证追加结果
file = open("test.txt", "r", encoding="utf-8")
print(file.read())
file.close()


# 6.用with自动关闭文件（推荐写法！）
print("=== 用with写入 ===")
with open("diary.txt", "w", encoding="utf-8") as f:
    f.write("2026年5月29日 晴\n")
    f.write("今天学了文件读写！\n")
# 离开with代码块，文件自动关闭，不需要手动close

print("=== 用with读取 ===")
with open("diary.txt", "r", encoding="utf-8") as f:
    print(f.read())


# 7.实战：通讯录数据保存到文件
import os

contacts = []

def load_contacts():
    """从文件加载通讯录"""
    global contacts
    if os.path.exists("contacts.txt"):
        with open("contacts.txt", "r", encoding="utf-8") as f:
            for line in f:
                # 每行格式：姓名,电话
                parts = line.strip().split(",")
                if len(parts) == 2:
                    contacts.append({"name": parts[0], "phone": parts[1]})
        print(f"已加载 {len(contacts)} 条联系人")
    else:
        print("通讯录为空，从零开始")

def save_contacts():
    """保存通讯录到文件"""
    with open("contacts.txt", "w", encoding="utf-8") as f:
        for c in contacts:
            f.write(f"{c['name']},{c['phone']}\n")
    print("通讯录已保存！")

def add_contact(name, phone):
    """添加联系人"""
    contacts.append({"name": name, "phone": phone})
    save_contacts()
    print(f"已添加：{name} - {phone}")

def show_contacts():
    """显示所有联系人"""
    if not contacts:
        print("通讯录为空")
        return
    print("--- 通讯录 ---")
    for i, c in enumerate(contacts, 1):
        print(f"{i}. {c['name']} - {c['phone']}")

# 测试运行
load_contacts()
add_contact("火鸟", "1351866756")
add_contact("小明", "13900139000")
show_contacts()

未经允许不得转载：百花谷博客 » 跟着AI学Python 第7课：文件读写