一、实践练习
练习1：简易日记本程序
python
import datetime
import os
class Diary:
def init(self, filename="diary.txt"):
self.filename = filename
def write_entry(self):"""写日记"""content = input("请输入日记内容：")timestamp = datetime.datetime.now().strftime("%Y-%m-%d %H:%M")try:with open(self.filename, "a", encoding="utf-8") as f:f.write(f"\n--- {timestamp} ---\n")f.write(content + "\n")print("日记保存成功")except Exception as e:print(f"保存失败：{e}")def read_all(self):"""阅读所有日记"""if not os.path.exists(self.filename):print("还没有日记")returntry:with open(self.filename, "r", encoding="utf-8") as f:content = f.read()print(content if content else "日记为空")except Exception as e:print(f"读取失败：{e}")def search(self, keyword):"""搜索日记"""try:with open(self.filename, "r", encoding="utf-8") as f:lines = f.readlines()results = []i = 0while i < len(lines):if lines[i].startswith("---"):date_line = lines[i]content = lines[i+1] if i+1 < len(lines) else ""if keyword in content:results.append((date_line.strip(), content.strip()))i += 2else:i += 1if results:print(f"找到{len(results)}条包含'{keyword}'的日记：")for date, entry in results:print(f"{date}\n{entry}\n")else:print("未找到相关日记")except Exception as e:print(f"搜索失败：{e}")
主程序
diary = Diary()
while True:
print("\n=== 简易日记本 ===")
print("1. 写日记")
print("2. 阅读全部")
print("3. 搜索日记")
print("4. 退出")
choice = input("请选择：")
if choice == "1":diary.write_entry()
elif choice == "2":diary.read_all()
elif choice == "3":keyword = input("请输入搜索关键词：")diary.search(keyword)
elif choice == "4":break
练习2：JSON配置管理器
python
import json
import os
class ConfigManager:
def init(self, filename="config.json"):
self.filename = filename
self.config = {}
self.load()
def load(self):"""从文件加载配置"""if os.path.exists(self.filename):try:with open(self.filename, "r", encoding="utf-8") as f:self.config = json.load(f)except (json.JSONDecodeError, FileNotFoundError):print("配置文件损坏，使用默认配置")self.config = {}else:print("配置文件不存在，将创建新文件")def save(self):"""保存配置到文件"""try:with open(self.filename, "w", encoding="utf-8") as f:json.dump(self.config, f, indent=4, ensure_ascii=False)print("配置保存成功")except Exception as e:print(f"保存失败：{e}")def get(self, key, default=None):return self.config.get(key, default)def set(self, key, value):self.config[key] = valueself.save()def show(self):if self.config:print("当前配置：")for k, v in self.config.items():print(f" {k}: {v}")else:print("配置为空")
使用示例
config = ConfigManager("app_config.json")
config.show()
while True:
print("\n1.查看配置 2.设置配置 3.删除配置 4.退出")
choice = input("请选择：")
if choice == "1":
config.show()
elif choice == "2":
key = input("键：")
value = input("值：")
config.set(key, value)
elif choice == "3":
key = input("要删除的键：")
if key in config.config:
del config.config[key]
config.save()
print("删除成功")
else:
print("键不存在")
elif choice == "4":
break
练习3：CSV成绩分析工具
python
import csv
def generate_scores_csv(filename="scores.csv", count=10):
"""生成随机成绩CSV文件"""
import random
names = ["小明", "小红", "小刚", "李华", "张伟", "王芳", "刘洋", "陈静", "赵磊", "孙丽"]
with open(filename, "w", newline="", encoding="utf-8") as f:
writer = csv.writer(f)
writer.writerow(["姓名", "语文", "数学", "英语"])
for i in range(count):
name = random.choice(names)
chinese = random.randint(60, 100)
math = random.randint(60, 100)
english = random.randint(60, 100)
writer.writerow([name, chinese, math, english])
print(f"已生成{count}条成绩记录到{filename}")
def analyze_scores(filename="scores.csv"):
"""分析成绩文件"""
try:
with open(filename, "r", encoding="utf-8") as f:
reader = csv.DictReader(f)
scores = []
for row in reader:
scores.append({
"name": row["姓名"],
"chinese": int(row["语文"]),
"math": int(row["数学"]),
"english": int(row["英语"])
})
if not scores:print("无数据")return# 统计各科平均分subjects = ["chinese", "math", "english"]subject_names = {"chinese": "语文", "math": "数学", "english": "英语"}averages = {}for sub in subjects:total = sum(s[sub] for s in scores)averages[sub] = total / len(scores)print("=== 成绩统计 ===")print(f"总人数：{len(scores)}")for sub in subjects:print(f"{subject_names[sub]}平均分：{averages[sub]:.1f}")# 找出总分前三for s in scores:s["total"] = s["chinese"] + s["math"] + s["english"]top3 = sorted(scores, key=lambda x: x["total"], reverse=True)[:3]print("\n总分前三名：")for i, s in enumerate(top3, 1):print(f"{i}. {s['name']}：总分{s['total']} (语文{s['chinese']} 数学{s['math']} 英语{s['english']})")except FileNotFoundError:print("成绩文件不存在，请先生成")
except Exception as e:print(f"分析出错：{e}")
主程序
while True:
print("\n=== 成绩分析工具 ===")
print("1. 生成随机成绩")
print("2. 分析成绩")
print("3. 退出")
choice = input("请选择：")
if choice == "1":
generate_scores_csv()
elif choice == "2":
analyze_scores()
elif choice == "3":
break
二、遇到的问题与解决
问题：写入CSV时出现多余空行
解决：open()时指定newline=''参数
问题：JSON写入中文变成Unicode转义序列
解决：json.dump(..., ensure_ascii=False)保留中文
问题：文件路径问题导致FileNotFoundError
解决：使用绝对路径或确保当前工作目录正确；也可使用os.path模块处理路径
问题：异常捕获顺序不当导致某些异常未被捕获
解决：先捕获具体异常，最后捕获通用Exception，避免except:裸捕获
问题：with语句中文件不存在时未处理
解决：将with放入try块中，捕获FileNotFoundError等
三、学习总结
文件操作是程序与外部数据交互的重要方式，with语句简化了资源管理
CSV适合表格数据，JSON适合结构化数据，是数据交换的常用格式
异常处理使程序更加健壮，能够优雅地处理错误情况
自定义异常可以提高代码的可读性和特定错误处理能力
文件操作与异常处理结合，可以构建可靠的数据持久化应用